Friday, July 25, 2014

Japanese Beetles and Roses--2014 Season

Well, it's late July and the Japanese Beetles (JBs) are just about at their peak here in Minneapolis. I would say we're seeing more than last year but not nearly as many as in 2012.  So does that mean it's getting better or worse?  In 2012, a golf course greens keeper told me that most golf courses in our area were using large amounts of imidicloprid (Merit) to protect fairways and greens from the JB grubs.  I attributed the downturn in last year's JB crop to be the result of that practice, since I have two golf courses within a mile of me, which is well within the JB flying range.  My best guess is that the golf courses probably used less imidicloprid in 2013 because of growing awareness that it is the most widely used of the neo-nicotinoid family of insecticides, which have been strongly implicated in bee colony collapse disorder and have been banned in Europe (imidicloprid is made by Bayer in Germany).  Also, I would assume there was less incentive to put it down on the golf courses, with such a sharp reduction in JBs during 2013.  Anyway, they're back again in force, so it's a good time to look again at the best ways to control them.

Here is a key passage from my 2012 article "The Beetles Are Coming, The Beetles Are Coming", as revised in January 2013:

.... Let’s take a look at how to try to control adult JBs on your roses.  Note I said “try” because there is really no completely satisfactory solution.  So, here’s the “secret” of this article: The best way to control JBs is with your fingers and soapy water!  Don’t be fooled by the easy solutions presented by insecticides; just like killing the grubs in your lawn, the JB adults you kill with insecticides are just the tip of the iceberg that is flowing up and down your street into your garden.  The only sure-fire way to deal with JBs is to pick or shake them off your roses into a can of soapy water.  JBs are really quite vulnerable to this method because their primary defense mechanism is to simply drop off the plant they are destroying, down to the dirt or grass.  They don’t sting or bite and they move pretty slowly, especially early in the morning and at dusk, so the “trick” here is to hold your can under the target JBs and pick or shake them off the plant into the soap-water.  I’m as squeamish as the next guy or gal about picking bugs with my fingers, so I wear nitrile surgical or milking gloves (that I get in the dairy-farm department at Fleet Farm) and I use a plastic 2 lb. coffee can (Maxwell House), which has a built-in handle and a big opening.  I squirt a little dishwashing soap in the can and fill it about half full with water.  The soap breaks the surface tension of the water and they are very helpless once they hit it.  While this process is laborious, especially because it goes on for many days, through thousands of JBs, there is some pleasure in watching the little demons meet their end, knowing that every JB I drown will never fertilize or lay an egg for next year’s hatch.  Each night, I dispose of the dead JBs either by flushing them down a toilet or putting them in my yard-waste bin (covered).  Note that they become very smelly if you leave them in the soap-water overnight.


This is important!  Don’t be tempted to squish JBs and throw them on the ground after you pick them off your roses (even though it would give you (and me) so much pleasure to do so).  When you squish a female JB her sexual-attractant pheromone is spewed out and brings in every male in the neighborhood!


Likewise, don’t buy JB traps.  They use that same sexual pheromone to bring JBs to the traps, and many more JBs come into your yard than ever find their way into the traps.  If you are just compelled to buy traps, buy them for your neighbors and keep them out of your own yard!  Oh, and be sure to empty your neighbors’ traps every day, because all those dead JB females just keep attracting more suitors, which are bound to find  your roses.  

Here's the address of the article.  There's a lot of good information there on JBs and, the last time I looked, it was also on the American Rose Society website.
http://jack-rosarian.blogspot.com/2013/01/the-beetles-are-coming-beetles-are.html

The main point here is that insecticides are really not the best answer for controlling JBs.  There is a very effective pyrethroid, that I mention in the article, but it also kills insects like lady bugs (they're beetles too) and other beneficials that eat aphids and thrips.  When you kill them off, you start a vicious cycle of insect infestation, which is far more difficult to control and a lot more work than a few weeks of drowning JBs!

I just issued a blog: "Controlling Spider Mites and Thrips on Roses Without Insecticides"
http://jack-rosarian.blogspot.com/2014/07/controlling-spider-mites-and-thrips-on.html .
So, if I were to spray a pyrethroid on my roses to deter the JBs now, I would negate all the work I describe in this article to introduce predatory mites and attract beneficial insects to my gardens.  I have not seen a single aphid in my gardens this summer because of the beneficials.  Last year, when I aggressively sprayed the pyrethroid for the JBs, I ended up with a major infestation of aphids.  Obviously, I had taken out all their enemies, so then I had to spray another insecticide to stop the aphids.  That's a vicious cycle, and all because I didn't want to drown JBs, i.e. lazy gardening.  What impresses me, however, is how well the beneficials have come back this summer, now that I'm not killing them off.  I really don't want to do that to them again.

As I meander through my rose beds, in the morning and evening (the best times), picking the beetles off the leaves and flowers and popping them in the soapy water, I carry a scissor and a bucket with me for disposing of the deadheads and damaged leaves that I cut off the roses, at the same time. In other words, I find that passing through the gardens several times a day causes me to do a better job of caring for my roses.  That side-effect of the JBs has become an important  part of my gardening routine.

So could JBs actually have a positive effect on a rose garden?  Well, that's a stretch!

Let me know if I can help.

Jack@falkerinvestments.com
@mnrosegardener


Wednesday, July 23, 2014

Controlling Spider Mites and Thrips on Roses Without Insecticides-- Part One

Author's Note: I started writing this blog in early June, when I decided that I was going to try and get through this growing season without insecticides, in order to attract and keep a population of beneficial insects in my gardens, which would attack the undesirables,i.e. two-spotted spider mites and thrips.  Frankly, I didn't want to publish this and then find that my methods weren't working. Well, here we are more than a month later and I'm very pleased to report that the only thing I've sprayed this summer is lots of water for the spider mites; plus I've imported from California large quantities of predatory mites (at least 100,000), nematodes (millions and millions), lady bugs (500) and minute pirate bugs (500) to attack both spider mites and thrips.  Bottom line: It's working!  In part one, I'll deal with spider mites, which are fairly simple to control with water and predatory mites, and then, in part two, thrips, which present a more complicated challenge.

Two-Spotted Spider Mites 

I've always had problems with spider mites. I've tried just about everything to get rid of them, but they just keep coming back.  I've spent a lot of money spraying miticides/ovicides, only to find that the mites are either not completely taken down, or there are still enough eggs hiding in and around the plants to start up new generations.  I have also known for years that water, sprayed in a sharp stream on the underside of plant leaves, is very effective in removing mites.  Once you knock the mites off the plants, they can't get back on and they die, so what's left on the plants are the eggs for the next generation.  I've been reluctant to do this, however, because water-washing 100-plus roses every three or four days (to hold down new generations of mites) has always seemed like a lot of work, plus it flies in the face of the conventional wisdom of not top watering roses.  Well, experience has taught me otherwise, and here's why.

I do a lot of propagation work, both with stem cuttings and air layering, and consequently I always have several plants under lights during the winter.  These plants always develop spider mites, which means I'm bringing mite eggs into the house on these cuttings/air layers.  And that proves that the miticides/ovicides I've been using aren't working.  I always wash these indoor plants with sharp streams of water in our laundry sink (which is messy when the plants start getting big) but, as long as I'm diligent about washing every three or four days, the mites go away.  So, I know washing works and I asked myself why I didn't just do that outside?

Miticides are expensive, especially those that contain ovicides to try and kill the eggs.  For example, an 8 ounce bottle of Forbid, a miticide/ovicide, which is the best product I've used because it's translaminar, meaning that it penetrates to the bottom of leaves to kill both the insect and its eggs, sells for $245, on sale from $289 at Rosemania.  That's more than $30 an ounce!  It works for a while, after a couple of applications (which it ought to at that price), but, as mentioned above, I've proven that the eggs are still there. I've also used Floramite, which has an ovicide in it but is not translaminar, and it really doesn't compare with Forbid in effectiveness, so it really has been unsatisfactory for me.  It's not cheap either, on sale at $119 for 8 ounces, down from $125, at Rosemania. Avid, which I used for many years, is just a miticide, with no control for the eggs.  This one needs to be sprayed every three or four days to kill successive generations of mites, and it works, if you are diligent, but really it does essentially the same thing as water, sprayed in the same regimen.  Avid isn't cheap, either, at $100 for 8 ounces.

The over-riding downside of these products is that they are relatively dangerous. You must wear protective clothing and you must wear a mask so you do not inhale them.  This is no joke. I had a bad experience, which caused lung problems for years.  Thankfully, it has gone away, but now I won't spray anything (except water) without a full-face 3M respirator and a Tyvek suit.  See my post on protecting yourself:
 http://jack-rosarian.blogspot.com/2013/02/hazardous-roses-2-protect-yourself.html

So, I asked myself this spring, after successfully controlling mites indoors with water all winter: Why don't I substitute a little sweat equity for all those expensive and dangerous chemicals on my shelf and just diligently wash the spider mites off my roses every couple of days this summer?  So that's what I've been doing for the last couple of months and I've been quite successful, although I'm still finding pockets of mites, as evidenced by a bud bending over here and there, which is a sure sign something is attacking the plant (see picture below).  On inspection with my magnifying glass, I invariably find webs and, after plucking that bud, I give the plant a special washing, paying special attention to all the buds and new growth on the plant.  This one, for example, had just a few webs on it but the damage had already been done.  This is also also a symptom of thrips or rose midge.



In the July-August 2014 issue of "American Rose", Rich Baer refers to this problem as "Funny Bud" and his "nonscientific conclusion" is that: "Funny Bud occurs when the normal development of the petiole is altered and the cells that are dividing to produce the petiole go astray and produce a leaf."   I think Rich is a great photographer but I beg to differ with his "nonscientific conclusion" here.  My experience is that funny bud is always an indication that the rose is under attack by insects (which, of course, could be what's making the petiole go astray).

Bottom line: Never leave a bud like this on the plant; get rid of it in a way that the insects can't spread. That's especially true of thrips and midge which have wings and will find their way to another plant.  Funny buds never produce good flowers and they need to go.

How to do it

The other day, I asked my good friend Susan Fox, rosarian par excellence in southern Illinois, what she does for spider mites.  After kind of growling into her cell phone, she said:  "I just spray them with a sharp stream of water; that's the only thing that really works.  None of the expensive miticides do the job as well as water".  I couldn't have said it better; so we're on the same page!

There's no secret about this either.  There are three or four mentions of this method in the July-August "American Rose" alone, including a quote from me in Susan's article: "Some Like it Hot".

I use several water spraying methods.  I have a great water wand that was advertised in the "American Rose" for many years by Walter Vinton in Springfield, MO.  It sprays a high-pressure fan of water directly upward, which allows me to get under each plant and work upward to the buds.  Unfortunately, Walter passed away and the product is no longer available. Here's how it looks:



I also use an old fashioned brass twist nozzle that is available in most hardware stores (as opposed to the big box stores, which seem to have lost track of such things).  Usually the sprayer head on watering wands is removable and you can replace it with a standard brass nozzle like this:

.
For my readers in Minnesota and Wisconsin, I found this wand at Menard's in Minneapolis ($7.99) and it actually makes a pretty good mite blaster, with the hose nozzle attached.  It is particularly effective in spraying the tops of the roses, i.e. the buds and new growth, and you can do it from a distance, if you see some evidence of mite damage.  You can vary the intensity and, with the curved tubing, you can also direct a sharp stream from the bottom of the plants (see photo below):




Early in the season, when the mites first appear, it's important to wash your roses at least every couple of days, for a few weeks, until all signs disappear. You can then revert to every four days or so, while paying special attention to hot spots, where mites seem to be the hardest to control.  Theoretically, the mites regenerate every four days from the eggs left on the plants and in the soil.  Remember, however, that there are likely to be several generations of spider mites in your garden, so they could be regenerating every day for a while, until you get them under control.  If you keep washing repeatedly, you should be able to kill off all succeeding generations, such that fewer new eggs are being laid.

And remember, at the same time, you're also washing aphids off your plants.  That's a plus!

Make no mistake, it's a lot of work to wash 100+ roses every two days, but it does ease up after a while, as you start to get control of the majority of the roses.  Hot spots on certain plants will remain and those need to be tended to every day or two.  If you see wilted or "crispy" leaves on new growth, that's a sign that mites are present (see a hot spot plant below).


I aggressively wash these wilted leaves and then all the new growth around them.  Then I pluck those leaves and throw them away.  They will die and become dry or "crispy", so there's no point in leaving them on the plant.  They will definitely not recover.  Note that the leaves below show no signs of mite damage; they are just on the new growth, so that's where I concentrate my washing efforts. The folks at Rincon-Vitova Insectaries in Ventura, CA, where I acquired my predatory mites, say they work from the bottom of the plant upward, forcing new generations of spider mites upward onto new growth.  That seems to be exactly what I'm experiencing, as in the above photo.  So all of my washing is on the new growth at the moment because that's where the damage is continuing; plus I don't want to wash off the predatory mites at the bottom of the plants.  Unlike spider mites, however, they can climb back on the plants and get back to work!

The downside of washing roses that are susceptible to black spot is that the fungus spores will eventually find their way onto the leaves from all the splashing.  Even though most of my roses are disease-resistant (by design), I am beginning to see black spot, here and there, in the third week of July, after two months of washing.  So, I'm about to spray a first round of Mancozeb (Manzate), which is the only fungicide that actually kills the spores, as opposed to just "controlling" them.  This will be the first time I will don my Tyvek suit and full-face respirator this year, so I'm quite pleased with the results of my no-spray efforts thus far.

For more information on treating black spot please see my July 2012 blog "There's a Fungusamongus":
 http://jack-rosarian.blogspot.com/2012/07/theres-fungusamongus.html  .

Finally, the upside of washing your roses on a hot summer day is that you get a little wet.  It always reminds me of running through the sprinkler when I was a kid; a very long time ago.  So it's fun work :)

Please feel free to ask questions about anything, either here on the blog page or directly by e-mail to:
jack@falkerinvestments.com .

In part two of this article, I will talk about my experience controlling thrips with beneficial insects and nematodes this summer.  It's working!

Good washing... and stay tuned to the Minnesota Rose Gardener.

Jack























Wednesday, March 5, 2014

What the Heck Was Wrong with this Winter?

For openers, before we dig into why it's been so cold in the Midwest this winter, let's take a look at what's really wrong with this winter around the world.  Here is a picture that Paul Douglas, Founder and CEO of WeatherNation, received from his great aunt, Eva Fels-Huber, in Cologne, Germany, along with her description of this winter in Western Europe:


"We are still waiting for winter to arrive.  We had spring-like temperatures since December 10th, 12C (53F) every day.  The birds are singing; my roses started blooming in mid-January." 


After Paul sent me this picture from his aunt, I sent an e-mail to a friend in Germany and asked her what their winter had been like this year.   Here is her response: 

“As for the winter here: we live between Mannheim and Heidelberg and didn't have winter at all. My sister in Bavaria said: some snow showers, that was it. Friends of ours in Eastern Germany said about the same. It is colder there than here, but no winter really.
In the middle of February I saw in Heidelberg meadows full of blooming daisies.  Now when you walk or drive around: everywhere daffodils and bushes and trees in yellow, white and pink.”


This is more the norm around the world than our cold weather in the Midwest.  Consider this statement from Paul Douglas' blog in the StarTribune:

"...Earth had its fourth warmest January.... According to NOAA, the combined average temperature over global land and ocean surfaces for January was 54.8 degrees Fahrenheit, which was 1.17 degrees above the 20th century average.  Using different analysis methods, NASA also concluded that Alaska had its third warmest January.... China had its second warmest January on record, and France tied with 1988 and 1936 for its warmest January."

Enter the Polar Vortex

So, tell that to gardeners in Minnesota and the whole Midwest.  If the earth is warmer than normal, how does that account for what seems to be one of the toughest winters in Midwest history? Here's a January 6th quote from Andrew Freedman of  the climate think-tank, Climate Central, that speaks to that question:

"Scientists said the deep freeze gripping the U.S. does not indicate a halt or reversal in global warming trends, either. In fact, it may be a counterintuitive example of global warming in action. Researchers told Climate Central that the weather pattern driving the extreme cold into the U.S. — with a weaker polar vortex moving around the Arctic like a slowing spinning top, eventually falling over and blowing open the door to the Arctic freezer — fits with other recently observed instances of unusual fall and wintertime jet stream configurations.

"Such weather patterns, which can feature relatively mild conditions in the Arctic at the same time dangerously cold conditions exist in vast parts of the lower 48, may be tied to the rapid warming and loss of sea ice in the Arctic due, in part, to man-made climate change.

"Arctic warming is altering the heat balance between the North Pole and the equator, which is what drives the strong current of upper level winds in the northern hemisphere commonly known as the jet stream. Some studies show that if that balance is altered then some types of extreme weather events become more likely to occur."

There is no question that the intrusion of the Polar Vortex is producing one of the worst winters in a long time for the Twin Cities and around the Midwest, including cities like Chicago, Detroit, Indianapolis and St. Louis. As a matter of fact, places like Detroit and Chicago have had worse winters, relatively speaking, than the Twin Cities. More about that later.  The real problem with the winter of 2013-2014, however, is not the depth of the cold, but the extent and continuity of it. We have currently had 50 below zero nights here and several more are predicted, which probably will put us in at least fourth and possibly third place, historically, for number of below zero nights in a winter season (the record is 60 in 1874-75, which we probably won't reach).

But it's important to note that we have had only one night this winter with USDA zone 4 cold.  It was -23 on January 6, 2014, which by no means was record cold for us.  In the 53 winters since 1962 the lowest temperature recorded has been -34 in 1970.  The rest of our below-zero temperatures this winter, despite how bad they felt, have been in zones 5 and 6.  Here's the breakdown: One below zero night in zone 4, 11 in zone 5, and the other 38 in zone 6.  So, while some people (especially some of  the TV weather people droning on about wind chills) would like to call this a record cold winter, it really isn't; it's just very long and miserable. And honestly it's wearing very thin with me, not unlike last winter, which was warmer, but also very long. Please read the conclusion of my blog: "How Winter Affects Roses" for my take on how an unreasonably long winter negatively affects roses:
http://jack-rosarian.blogspot.com/2013/12/how-winter-affects-roses.html

People in Minnesota are so naturally self-effacing about winter that they tend to think this is happening only to them: "Uff Dah, it's why we tip our roses, don't ya know" Not! As noted above, we have had just one night in zone 4 (and just barely), considering that 12 of our winters since 2000 have been in zone 5.  With that in mind, let's take a look at how other Midwest cities have been affected.

  • Detroit and Ann Arbor, where I grew up and went to college, have almost always been in zone 6, in the lee of the Great Lakes. Since 2000, six of Detroit's winters have been in zone 7 (i.e. not even below zero) and the rest in zone 6. This winter, their low temperatures have been -14 and -12, i.e., two nights in zone 5; twelve nights in zone 6, and the rest in zone 7.


  • Chicago, which has had all but one of its winters in zone 6 or above since 2000, had a low of -16 in January, with a grand total of four nights in zone 5.  That's a bigger variance than either Detroit or the Twin Cities.


  • St. Louis, which has been in zone 7 every year since 2000, with one exception when it was in zone 8, saw a low of -8 this winter, with a total of four nights in zone 6; a big variance for them.


  • Indianapolis, which has had seven winters in zone 7 and five in zone 6, since 2000, saw two nights in zone 5 this year, with low temperatures of -15 and -14; another big variance.

The Polar Vortex 

So what exactly is the Polar Vortex?  Here is a good explanation from an NBC News piece from early January:

"The polar vortex is basically a great swirling pool of extremely cold air located tens of thousands of feet in the atmosphere.... Basically an arctic cyclone, it ordinarily spins counterclockwise around the north and south poles.  While it tends to dip over northeastern Canada, it's catching everyone's attention because it has moved southward over such a large population....Why has it traveled so far south? Chiefly, warmer air builds up over areas such as Greenland or Alaska and that air forces the colder, denser air southward.... "

And here is a statement that Paul Douglas prepared for this blog post:

" I remember some very cold winters in the mid and late 70s, but even then there was more variability in the jet stream, more fluctuations and mild periods in between arctic blasts. What is unique about this winter, in my opinion, is the persistence of this blocking pattern. We’ve gone nearly 3 months in a row with little variation in the jet stream over North America. This mirrors a larger (global) trend of slower jet stream winds over northern latitudes and more of a tendency for “blocking” patterns, where weather slows or even stalls for days or weeks at a time. Jennifer Francis at Rutgers has done some research on this “polar amplification”, theorizing that rapid warming of the Arctic and far northern latitudes is disrupting north-south temperature extremes, which, in turn, may be impacting jet stream winds, with more of a tendency for weather to become locked or “stuck”.

“ I've been tracking weather for over 40 years and I can’t remember a winter quite like this, the sheer persistence of the pattern to remain more or less stuck in place. Western drought, numbing cold east of the Rockies, with historic flooding for Britain and record warmth for much of Europe – it’s all interconnected. More research is required to confirm whether rapid warming in far northern latitudes (and summer ice melt in the Arctic) is, in fact, having a domino effect at our latitude, but with each passing year the weather is becoming more unusual, more extremes, more “weather-whiplash” (flood to drought, etc) and more volatility in general. I tell people the truth: we are changing the chemical composition of the atmosphere, conducting an experiment that’s never been done before. CO2 levels are at 400 ppm, higher than any time in the last 800,000 years. We’re poking at Earth’s climate system with a long, sharp stick and then acting surprised when the weather comes back to bite us.


Here are graphics that show the Polar Vortex incursion in the central U.S.  Note especially the warmer than normal zones in the Alaska and Greenland areas, which are responsible for pushing the jet stream and polar air southward:










The 64 trillion dollar question, so to speak, is whether this polar vortex incursion, caused by the unprecedented warming of the arctic regions, will reoccur in the years ahead.  There seems to be a fairly high probability that we will see it again but it seems to me that, as the earth continues to warm over the years, it may not be as extreme, i.e. the polar air will be warmer (not a good thing for the earth).  Consider again what Paul Douglas told us:

"... We are changing the chemical composition of the atmosphere, conducting an experiment that’s never been done before. CO2 levels are at 400 ppm, higher than any time in the last 800,000 years. We’re poking at Earth’s climate system with a long, sharp stick and then acting surprised when the weather comes back to bite us."

I am also a great believer in statistical trend lines, and the extreme minimum temperature (EMT) trend lines that I have plotted for almost all Midwest cities, for the years since 1962, show that we are all on a steady trend toward higher winter temperatures.  The Twin Cities' EMT trend line shows conclusively that we have moved into zone 5 and are on our way to zone 6 in just a few years.  One night of marginally zone 4 temperatures in 2014 certainly does not change the upward slope of our trend line in a meaningful way, so it is statistically reasonable to assume that we will continue to see warmer EMTs in the years ahead.

But, to use Paul's analogy, who knows what will happen when we poke the earth's climate system with a long, sharp stick?  My statistical prognostications for a warmer winter this year were certainly wrong and one of my good friends took the opportunity last week to give me a gentle push into a snow bank at Bredesen Park in Edina, as retribution.  Here is the Minnesota Rose Gardener making a snow angel in two feet of snow!



Finally, Twin Cities meteorologist, Jonathan Yuhas, (with tongue in cheek I'm sure) posted the following graphic on Facebook.  Notice any similarity to the polar vortex graphics above?  Oh well, smell the roses while we can; maybe sometime in July this year.


Jack Falker
March 5, 2014

Tuesday, February 4, 2014

Winter-Protecting Roses with Construction Blankets


This blog post is a joint effort between Deb Keiser, Rose Specialist at the Munsinger and Clemens Gardens in St. Cloud, Minnesota, and Jack Falker, “The Minnesota Rose Gardener”.

In the last few years a new method of winter-protecting roses has emerged in Minnesota, which we believe has application beyond the so-called “cold zones” of the Upper Midwest.   At the Virginia Clemens Rose Garden in St. Cloud (Zone 3/4), Rose Specialist Deb Keiser has stopped using the “Minnesota Tip” method and is now winter-protecting both her public and personal rose gardens with the insulated blankets cement contractors use in the winter to cure concrete in sub-freezing temperatures.  Construction blankets typically come in 6 X 25 or 12 X 25 foot sizes and have an insulating R-value of 7.5.  (We believe the R-value is important and blankets with less than an R 7.5 value may not be as effective.)

In earlier articles on preparing roses for winter: “Winter Protecting Your Roses”
(http://jack-rosarian.blogspot.com/2013/09/winter-protecting-your-roses.html) and “How Winter Affects Roses” (http://jack-rosarian.blogspot.com/2013/12/how-winter-affects-roses.html), I have advocated the following sound horticultural practices, in lieu of the labor-intensive Minnesota-tip method.
  • Plant the bud unions of hybrid tea roses 3-6 inches below the soil surface and the crowns of own-root roses at similar depths to protect from freezing and thawing. 
  • Give your roses a six-week potassium feast to harden off their canes for winter.
  • Use at least 3 inches of wood chips in your beds, year-round, and more around your roses in the fall.
  • Mound your roses with good compost in the fall, including lots of coffee grounds.
  • Tie up your roses in bundles and cut them back to about 8-12 inches, when they stop blooming.
  • Strategically place rodent bait containers around your roses to protect against vole damage.
  • Cover your roses with half-filled leaf bags or wire cylinders of leaves, when the ground first freezes or snow begins to accumulate, whichever comes first.  Hay can also be used for this purpose if it is packed closely around the mounded plants and held in place by bags or fencing.  Straw is less effective because it is less substantial and does not compost well.
  • Construction blankets are our other alternative, as we will discuss below.
The final steps above insure that your roses will not freeze and thaw repeatedly during the winter.  In the "warmer" cold zones, i.e., zones 6 and 7, insulating your roses, as described above, should have the effect of not allowing them to freeze in the first place; different than our expectation in zones 3, 4 and 5.

Enter Construction Blankets!

Deb and I agree on virtually all of the above steps, but she believes that using construction blankets, instead of leaves or hay, for the final protective cover in the fall is a better solution.  Seeing is believing, and I believe that Deb's practice, which she has been using for upwards of ten years now, has applicability not only in zones 3, 4 and 5, where the ground freezes solid every winter, but especially in zones 6 and 7 where constant freezing and thawing is endemic to most winters.

In late October, when the roses have stopped blooming (perhaps early November in Chicago or early December in zone 7), Deb mounds her roses and cuts them back, as mentioned in the bullet points above. If it is dry, you can continue to water the plants or, if you are still in the process of applying liquid potassium (which we highly recommend), that watering will suffice. Deb puts the blankets on her roses just before night-time temperatures go into the low 20s or snow starts to accumulate, whichever comes first.  This is all very similar to the practices cited in the bullet points above. 

For those of you not accustomed to cutting back your roses in the fall, please be assured that there is no downside in doing this, when they have finished blooming.  When roses are well mulched and protected all winter, they grow very aggressively in the spring, which is the strong growth you really want for the new season ahead (see the spring pictures of Deb's garden below).

Here is how the Virginia Clemens Rose Garden looks after Deb has cut everything back and begun covering with the construction blankets.  Note that she is careful to secure the blankets around the roses with lots of bricks.



And below is a picture of the Virginia Clemens Rose Garden fully covered.  Note that some of the trees still have a few leaves, so you can gauge the equivalent time where you live.  It starts to get cold in St. Cloud in mid-November, so Deb is striving to get everything covered, before the nights go into the low-twenties .  By the way, those Minnesota rosarians who still tip their roses are digging trenches and tipping their roses into them in mid to late October, which seems early to us, given that their roses have often not finished blooming, but that's how that process works.


And below is a picture of one of Deb's home rose gardens, taken in 2 degree weather on November 23, 2013. Note that 2 X 4s can be used to secure the blankets, as well as bricks.  All of this disappears, of course, once the snow covers everything.



And the Ground Doesn't Freeze!

Given the fact that the ground freezes several feet down in a typical Minnesota winter, regardless of snow cover, and that both mounded/leaf-covered roses and Minnesota-tipped roses are thereby frozen solid and simply protected from thawing and refreezing, I naturally assumed that the Virginia Clemens beds above would be similarly frozen and protected from thawing until spring.  I was, therefore, somewhat skeptical when Deb and her husband Dave Keiser told me in mid-January 2014, at the Twin Cities Rose Club meeting, that they believed neither the roses in the Clemens gardens nor the roses in their personal gardens were frozen under the construction blankets.  Keep in mind that the low temperature had already been -25 F in St. Cloud this winter and that there was more than a foot of snow on the gardens.

So, knowing that we were going to jointly write this article, Deb suggested that we should clear away the snow from the corner of one of the above beds and take a peek under the blanket.  That sounded like a fun way to play in the snow and, since the temperature was actually going to moderate for a day or two, I drove up to St. Cloud on January 24th and we initiated our little experiment with a couple of shovels and a commercial-grade thermometer to measure soil temperature under the blankets.  Here are pictures of the two of us "gardening" on that +30 F, late-January day:




 Here's Deb clearing away the snow from the edge of the covered bed.



Here's Jack reaching as far under the blanket as possible with the thermometer.  This is where we discovered that the ground was actually loose and friable under the blankets.  


We were actually able to stick the thermometer a couple of inches into the unfrozen ground and found it to be 33 and 34 degrees, in two separate measurements.

This is an impressive result, given that we were measuring a zone 3/4 garden in January, when the low temperature had been -25 F.  Interpolating this result to "warmer" cold zones such as 5, 6 and 7, it is easy to see how using construction blankets would be a relatively easy, sure-fire way of protecting sensitive rose gardens in any winter weather situation, perhaps especially in the warmer cold zones that experience constant freezing and thawing all winter.

Here are Deb's comments about what she is winter-protecting in both her personal and the Virginia Clemens gardens:  

"... At home I cover zone 6 & 7 grafted hybrid tea, floribunda, grandiflora, and shrub roses, a few own-root hybrid tea roses, miniature roses, zone 5 Flower Carpet shrub roses and David Austin English roses, Tess of the d'Urbervilles and Benjamin Britten.... At work I cover zone 6 and 7 grafted hybrid tea, floribunda, grandiflora and shrub roses, some own-root hybrid tea, floribunda and shrub roses, miniature roses, a bed of David Austin English roses, a bed of Buck roses and Knock Out roses...."

Deb further points out that all of her grafted roses are planted with their bud unions about 3 inches below ground level.  This is very important in any garden that experiences even the mildest of winters.  In our considered opinion, there is no justification for planting grafted roses with bud unions above ground level in any garden location.

Incidentally, Deb also puts potted miniature roses and tender perennials under the blankets in the Clemens garden.  If the pots are too large, the plants can be removed from their pots, laid on their sides, and mulched before covering with the blankets.  While Deb currently brings all of the garden's potted tree-rose "standards" into the garden's greenhouse, she believes that standards could be wintered under the blankets, as well, so long as the plants are laid on their sides and fully covered with mulch, before the blankets are applied.

And here's the proof of the pudding: pictures of Deb's gardens in early spring, when the blankets come off. Note that the roses have already started to grow under the blankets; ready to prune and take-off toward their first bloom cycle.  Once again, for those of you in the warmer cold zones, we do not believe there is any disadvantage in cutting your roses back and covering them thoroughly in the fall.  




Construction blankets are in common use by cement contractors in just about any area that experiences winter weather.  Apparently, most contractors rent their blankets, as required, and the best place to acquire them, either used or new, is likely to be rental companies that cater to those contractors.  Perhaps the best reason for this is that the blankets have to be stored someplace dry for more than six months of the year, which presents a potential storage problem for both contractors and gardeners alike. In Deb's case, she acquires most of her blankets in good, used condition from a rental firm in St. Cloud.  She also has the distinct advantage of having several, roomy, municipal buildings for storing her Virginia Clemens blankets in the summer time.  I might also mention that the Munsinger and Clemens Gardens, have a beautiful, large, new greenhouse, in which a large variety of roses and many other plants are profusely blooming all winter long. So who needs winter protection in Minnesota, when you have a climate-controlled greenhouse?  But that's another story altogether!

Both Deb and I would be happy to answer any questions you might have. 

You can reach Deb at deb.keiser@ci.stcloud.mn.us;
and you can reach Jack at  jack@falkerinvestments.com .

Deb Keiser and Jack Falker
February 4, 2014


Friday, January 24, 2014

How Windchill Affects Roses

Yesterday, we woke up in Minneapolis to a temperature of -17 F, with a windchill of -36 F . Every TV weather-person in town was wide-eyedly proclaiming the dangerous windchill temperatures, to the point, I'm sure, of scaring the average person, who had to go out of the house to work or school, half out of their wits. In fact, every school district cancelled school for the second time this winter, due to the windchill temperature.  Our most sophisticated local (and national) meteorologist, Paul Douglas, posed in his blog yesterday his rhetorical question of whether they cancel school for windchill temps in Canada?  It's no wonder people start believing that the temperature really is -36 in Minnesota, when -17 is quite bad enough.

Question: What temperature do you think our roses were "feeling" yesterday morning?

Simple Answer: -17 F.  Neither roses nor any other plant experience any temperature other than the actual ambient temperature.  And -17 is plenty cold, thank you very much.

Here's a good quote from a National Weather Service article about windchill:

"Wind chill is the term used to describe the rate of heat loss on the human body resulting from the combined effect of low temperature and wind.  As winds increase, heat is carried away from the body at a faster rate, driving down both the skin temperature and eventually the internal body temperature.  While exposure to low wind chills can be life threatening to both humans and animals alike, the only effect that wind chill has on inanimate objects, such as vehicles, is that it shortens the time that it takes the object to cool to the actual air temperature (it cannot cool the object down below that temperature)."

Here's that whole article

http://www.crh.noaa.gov/ddc/?n=windchill


Here's another good quote from a Kansas State University article:

Plants Don’t Care if the Wind Chill Tanks

"When wind chill temperatures plummet, gardeners chafe about their landscape and fruit plants' odds for survival.  Some gardeners worry too much.... Cold can be a killer if people are growing marginally hardy plants or if air temperatures drop well below what's usual where they live.  Hard freezes are particularly destructive when plants aren't fully dormant.  But cold and wind chill aren't the same thing.  Wind chill only affects warm-blooded animals -- including people.  It's an indexed, scientific measure of how wind speed and air temperature combine to impact animal heat loss.... We know, for example, that our heat-loss rate will speed up as the air temperature drops.  The faster the wind is blowing, however, the more dramatic that heat loss is going to be .... Wind chill has no meaning for plants.  Unlike warm-blooded animals, they don't try to maintain a particular body temperature year-round".

And here's that whole article:

http://www.ksre.ksu.edu/news/story/wind_chill121709.aspx

Of course, we know that  roses feel the winter cold and die back according to the level of protection afforded them.  And winter-winds do, of course, have an effect on that die-back, desiccating the canes, but the important thing to understand is that wind does not make a plant "feel" colder than the actual temperature, even though it shortens the time it takes for the plant to reach that temperature.

Here's an example: Suppose that the ambient temperature is 35 F and the wind is blowing 30 MPH. According to the chart in the NWS article (above), the wind chill is 22 F.  So are your roses freezing?  Or, better yet, are the puddles in your garden freezing?  Of course not, because the freezing point of water is 32 F.  However, if you go out in your garden without a hat and jacket, you will feel like it is 22, not 35, because of the combined effects of the cold temperature and the high wind on your flesh.

Another example of the effect of wind chill on the human body is to go back to yesterday's -17/-36 situation.  If I go out for a walk, as I usually do in these temperatures, any exposed skin (like my nose) will be frostbitten in about five minutes because of the -36 wind chill.  That is a serious problem, especially for children waiting for school buses or people who have to work outdoors.  Children are notoriously bad at covering-up in cold weather and, thus, it is probably wise to cancel schools (in Canada too).  And, while my plants certainly are not feeling the wind chill, the old Minnesota Rose Gardener certainly is, so he has to dress accordingly in his thinsulate-lined parka and antarctic mask.

The temperature was about -2 and the wind-chill about -15 when this picture was taken.
Cold enough for ya?  It sure was for me!

So, bundle up and make sure your roses get the right winter-protection each winter.  See my blogs "Winter Protecting Your Roses":

http://jack-rosarian.blogspot.com/2013/09/winter-protecting-your-roses.html

and "How Winter Affects Roses":

http://jack-rosarian.blogspot.com/2013/12/how-winter-affects-roses.html

Jack Falker
January 24, 2014










Saturday, January 11, 2014

Deb Keiser's Reflections on the 2013 Growing Season

The following  is a guest post from Deb Keiser, Rose Specialist at the Virginia Clemens Garden in St. Cloud, Minnesota.  Deb is a Twin Cities Rose Club member and, in my opinion, one of the most knowledgeable rosarians in the country.

In my last "Minnesota Rose Gardener" blog, "How Winter Affects Roses", I described an unusual situation that occurred in 2013:

"Even though our winters are warmer, in terms of extreme minimum temperatures (EMT), they seem to be just as long, or perhaps even longer in certain years, thereby keeping our roses frozen for a longer period of time. For example, our ground (and therefore our roses) stayed frozen into late April or early May in 2013, and we had snow on the ground into early May.  This is 2-4 weeks later than normal. What happened in May, once the ground thawed out, was that the roses had a very hard time getting started and there seemed to be more die-back than usual, even with shrubs that are zone 3 and 4 hardy.... In other words, with a 2013 EMT of -13 (well above the median for zone 5), our roses actually seemed like they had been through a much harder winter.  So it would appear that the length of time roses are frozen, not just the low temperature in a given year, impacts survivability.  After all, if you think about it, frozen is frozen; the only thing that happens with a lower temperature is that the ground freezes deeper and the roses take longer to thaw out and start growing in the new season.  But what happens to them when the winter is so long that they can't start growing again in a timely way?"

Here is Deb's description of what happened in the Clemens garden in 2013, including the loss of 12% of their roses, which is highly unusual for a professionally run garden that uses state-of-the-art winter protection methods. It is eerily similar to what many, if not most, Minnesota rosarians experienced in 2013.


Mid December Reflections on the 2013 Growing Season
By Deb Keiser, Clemens Garden’s Rose Specialist

The weather in April and May 2013 will be remembered as “extreme” and “record-setting” in many parts of the United States. St. Cloud, MN was no exception to this. We broke several long-standing records and experienced extreme weather fluctuations.

To plan for the date that our garden staff will uncover the construction blanket covered roses at Clemens Gardens, I often start watching the forecast high and low temperatures near the beginning of April, with a target date of the week of April 15th as the estimated time for the actual uncovering. With widely fluctuating weather this past April, Mother Nature kept us anxiously waiting and watching for warm weather for quite awhile. On April 11, 2013, St Cloud received 8.7 inches of snow. The high temperature on April 15, 2013 was 36 degrees. We had freezing temperatures every night that week. On April 18, 2013, we received another 9.4 inches of snow and we set a new record for most snowfall in April with a total of 24.4 inches for the month. On April 20, 2013 we set a new record with a low temperature of 16 degrees in St. Cloud.  I knew it would take awhile for the snow to melt with temperatures like that, so I set my new target date for May 1, 2013. Then on April 27th, we had a high temperature of 74 degrees with a low that day of 30 degrees. Crazy weather indeed! April 28th brought us a 77 degree day followed by a couple of days in the low 70’s which made uncovering the roses seem very tempting, except for the 10 day forecast. Just when we thought it was finally safe to uncover the roses, an early May snowstorm dropped a record-setting 18 inches of snow on parts of southeastern Minnesota. In St Cloud, we were fortunate not to get snow but we did have high temperatures in the low 40’s, a low of 28 degrees, and ¼ inch of rain from May 1st thru 4th. With a rose pruning day for volunteers scheduled for the evening of May 6th, a high temperature of 72 degrees that day and 70 degree temps forecast for the week, I decided that we could finally uncover the roses. As luck would have it we experienced freezing low temperatures the following weekend, followed by a high of 95 degrees two days later. Only in Minnesota! If you don’t like the weather, just wait awhile and it will change!

Here is a re-cap of the 2013 rose growing season at Clemens Gardens, highlighting some of our achievements and some of our misfortunes.

Misfortunes –

When uncovered, the tender roses in the Virginia Clemens Rose Garden looked alive but not leafed out as in past years. This was probably due to the late cold temperatures in April and May, prior to uncovering them. This made for a late first flush – July 4th weekend, as compared to a Memorial Day weekend first flush in 2010, a June 20th first flush in 2011, and a mid-May first flush in 2012.

Our pruning season started late, our weather warmed up fast, and it was off to the races to try to get over 1,800 roses pruned before they were totally leafed out. With only one assistant and a handful of volunteers, we were still pruning roses in mid-summer.

We lost 140 hybrid tea and floribunda roses in our 1,200 rose Virginia Clemens Rose Garden, or about 12%. Fortunately, most of the roses were older roses that were in the gardens prior to when I started working here in 2004, and some were donated packaged roses from 2006 and 2007. The roses were probably weak to begin with from the 31 days of 90 plus degree heat and drought conditions in July 2012. The late cold weather after uncovering them did not help either.

Due to the late start to the season our Bob’s Mix fertilizer was applied much later than normal. The weather at application was hotter and drier then usual. We did not see a big growth spurt in the roses until we had rain and cooler temperatures late in the season. The roses were much shorter than normal and did not produce as many blooms.

Our Award of Excellence (AOE) miniature rose trials entries for 2013 arrived the week of April 25, 2013 and had to be repotted and grown in the Munsinger & Clemens Gardens’ greenhouse until it was warm enough to plant them outdoors. They were moved out to the AOE trial garden later than normal, which meant less time for the AOE Evaluators to evaluate them.

Achievements –

The long cold spring gave our 95 new roses from Weeks Roses, our five shrub roses purchased from Twin Cities Rose Club’s fundraiser, and our sixteen 2013 AOE trial miniature rose entries plenty of growing time in pots in our 10,000 sq ft greenhouse.

We received plenty of moisture early in the 2013 season to get the uncovered roses and hardy shrub roses started growing well in the garden beds.

The shrub and Old Garden roses that we moved from UMORE garden in October 2012 and planted in our lower rose garden, came through the winter very well with only compost for winter cover. I was pleasantly surprised at the winter hardiness of the zone 4b & 5 roses – four ‘Double Knock Out’, seven ‘Carefree Marvel’, and two ‘Salmon Impressionist’. All of the shrub roses from UMORE grew and bloomed well during 2013. The ten plants of ‘Winnipeg Parks’ which were planted on the rock walls bordering the front and south side of the Virginia Clemens Rose Garden were constant bloom producers. I heard many visitors commenting on their beautiful large pink flowers. The OGR divisions off of the UMORE “mother” plants experienced nice growth and may bloom for the first time in June 2014. I look forward to seeing all of the spinosissima, gallica, alba, & moss roses in bloom.

The shrub roses in our Lower Trial Rose Garden proved their winter hardiness by surviving the winter with only a 4 inch layer of rice hull mulch and snow cover for winter insulation. These include ‘Pink Home Run’, ‘Carefree Sunshine’, ‘Peppermint Pop’, Northern Accent roses ‘Ole’, ‘Lena’, ‘Sven’, and ‘Sigrid’, Easy Elegance roses ‘Little Mischief’ and ‘Sunrise Sunset’, ‘Carefree Wonder’, ‘Como Park’, ‘Thrive!’, ‘The Charleton’, and Kathy Zuzek’s trial roses. Blackspot was not a problem in the Lower Trial Garden, even though the rice hull mulch had been wintered over from the previous season. The shrub roses were very disease free this season.
  
We replaced most of the soaker hoses in the Virginia Clemens and Upper Trial Rose Gardens with new ¾ “ Osmile double-thick wall soaker hoses with a lifetime guarantee. The hoses were put in place prior to the hot, dry weather in July and August. They worked very well during the season with much better water output than the older hoses. The best thing was no more fixing broken soaker hoses. We will replace the rest of our soaker hoses next summer.

Although it was later than normal when we planted our new potted roses from Weeks, Twin Cities Rose Club, and AOE entries outdoors, they transplanted and grew well. Many of the plants were already in bloom and were good sized plants when planted outdoors. I was especially impressed with the three test roses that Weeks sent us. All three plants grew well and their blooms quickly became noticed by visitors. The large golden orange long-stemmed blooms of hybrid tea rose ‘Good As Gold’ and the large fragrant bright yellow old-fashioned blossoms of grandiflora rose ‘Happy Go Lucky’ seemed to put on a constant display. Both were very disease resistant. Although grandiflora rose ‘Coretta Scott King’ with its beautiful long coral and white buds and disease resistant foliage did not bloom as much as the other two test roses, its big clusters of blooms were very long lasting.

In early July, we purchased 16 very nice large potted hybrid tea and floribunda roses from Linder’s Greenhouse during a 50% off sale and 24 own-root hybrid tea and floribunda roses on sale from Roses Unlimited. They performed well and added many older varieties that are new to our gardens. The three plants of floribunda ‘Oh My!’ with its dark velvet red blooms and the bright red blooms of hybrid tea roses ‘Olympiad’ and ‘In the Mood’ from Linders Greenhouse put on a good display along the Upper Trial Garden walkway through the Clemens Rest Area Garden. The two pink bloomed ‘Sexy Rexy’ floribunda roses and the two ‘Estelle’ hybrid tea roses with their florist quality russet blooms reversing to yellow drew many comments from visitors to the Virginia Clemens Rose Garden. Both were purchased from Linders. We were sad to hear of the closing of Linder’s Greenhouse. They were a generous donor of many good quality roses to our gardens and a good source of quality plants and shrubs for Minnesota gardeners. They will be missed!

We only had one week of 90 plus degree weather in mid July and another week of  90’s at the end of August. Unfortunately, it was during the MN State Fair. Most of our July, August, and September temperatures were in the mid 70’s to low 80’s, which made for wonderful working conditions at the gardens. Our rainfall was below normal but the new soaker hoses worked well. We fertilized the roses with Alaska Morbloom fertilizer 0-10-10 after August 31st and the roses continued to bloom and grow.

In September and early October, we gave the Virginia Clemens and Upper Trial Garden roses doses of potassium sulfate 0-0-50 to help ready them for winter. I chose potassium sulfate with the hopes of lowering our soil PH from almost 8. We also treated areas of the Virginia Clemens Rose Garden, where our roses were experiencing growth problems, with fast-acting sulfur (calcium sulfate) also with the intent to lower the PH in those areas to improve growth for 2014. I will be checking our soil PH again next spring and adding amendments as necessary to correct our PH.

Winter came early with cooler than normal temperatures in mid October, so we started our winter protection process of cutting back the tender roses to 8 inches of height. This allows us to cover the rose beds tightly with insulated construction blankets. We mulched the roses with two large scoops of finished compost over the crown and extending out to the sides of the rose plant.  With temperatures threatening to drop into the teens at night, we applied insulated construction blankets to the rose beds in the Virginia Clemens and Upper Trial Rose Gardens on November 7th and tucked our roses in for their long winter’s nap a few days earlier than in past years. So far this winter, we have had a good amount of snowfall to add additional cover to the rose beds.



Now we plan for next season with the hope of an earlier start in the spring with less winter damage, followed by adequate rainfall and warm sunny days for good growth, and an insect and disease free season. One can only hope that Mother Nature is good to Minnesota gardeners next year!

As always, let Deb and me know what you think.




Friday, December 27, 2013

How Winter Affects Roses

This is a revision of my 12/27/2013 post, based on several good comments I have received from Dr. Gary Ritchie and a number of other readers.  Thanks for the enthusiastic responses from so many rosarians, whom I hold in high esteem.
 JRF 12/29/2013

At the peak of winter here in the cold zones, our roses are "winter protected" to help them survive the sub-zero temperatures of USDA zones 4, 5, and 6.  Most folks look out at their roses covered (hopefully) with a nice layer of snow and believe their roses are dormant; just waiting to thaw out, break dormancy and start growing again.  But wait....  Did you know that only species roses, such as Rosa Rugosa, Rosa Glauca, Rosa Gallica etc. go through a dormancy cycle and that all modern, repeat-blooming, "remontant" roses do not?  So what's going on here with modern roses in winter?

Before I try to answer that question, I want to say that I recently learned much of this from "Dormancy in Roses", an excellent four-part series in the American Rose, during 2013 and early 2014, by Dr. Gary Ritchie of Olympia, Washington (see footnote below).  I will quote Gary several times in this post and want to give him full credit for his research and opinions.  However, I also want to note that Gary's articles have raised some important issues for me, based on my many years of successfully growing modern roses in Minnesota; in particular, why keeping modern roses frozen hard in the winter is what keeps them alive, rather than killing them outright. This seems somewhat contrary to the conclusion of Part 4 of Gary's article, where he says:

"I've not seen data on specific cold hardiness of modern roses but experience indicates that it is modest at best. So, while we enjoy continuous bloom throughout the summer, we face the annual chore of winter protecting our roses.  Here in the moderate coastal Northwest, this requires no more than mounding up our plants in fall.  But in more extreme climates winter protection can be much more difficult and problematic -- sometimes even requiring burying the plants underground to assure their over-winter survival." 


Here is how I would re-phrase Gary’s quote (above) from my perspective in zone 4/5:

"I've not seen data on specific cold hardiness of modern roses, but experience indicates that, with good winter protection, most modern roses, including budded hybrid-teas, are very cold-hardy, as long as they are allowed to freeze solid and stay frozen all winter.  Here in Minnesota (zones 3, 4, and 5), winter protection begins with planting bud unions four to six inches deep, mounding with dirt or compost in the fall, and subsequently winter-protecting with leaves or hay after the ground freezes in late fall or early winter. Another alternative is the Minnesota Tip method of burying plants underground.  Both methods have as their objective keeping roses frozen throughout the winter; not to keep them from freezing, which is virtually impossible in our zone 4/5 winters."  (JRF Quote)

In other words, the whole purpose of winter-protecting roses in the cold zones, where the ground freezes from several inches to more than a foot down, is to keep roses from repeatedly freezing and thawing. The only exception to this might be the use of insulated R7.5 construction blankets, which are gaining popularity in Minnesota.  My friend and TCRC mainstay, Deb Keiser, who manages the Virginia Clemens Rose Garden in St. Cloud, believes that putting construction blankets down before the ground freezes keeps her roses from freezing in the first place (which is quite an achievement in St. Cloud!). But the principle is the same, whether the ground freezes under the blankets or not:  i.e., to keep your roses from repeatedly freezing and thawing.  This can be problematic here in the Twin Cities (now in zone 5) and even more so in zones 6 and 7, where mid-winter thaws are more frequent.  Take a look at my recent article on winter protection:

http://jack-rosarian.blogspot.com/2013/09/winter-protecting-your-roses.html


Here is how two of my rose beds looked on Christmas Day 2013:

Buck Earth Songs under a foot of snow insulation


Terraced Canadians and Bucks


Now, just in case I have given the impression that I'm not growing hybrid teas in Minnesota winters, here is my winter-protected Elina on a -2 F. afternoon in Edina.  The reason the leaf bag is showing under the snow is that we had a record-breaking 48 F. the day before I took this picture; a 50 degree swing!  And that's what winter protection is all about in zone 4/5: to keep the roses from thawing and re-freezing in these crazy temperature swings!

Above: Elina in a Minnesota Winter

Dr. Gary Ritchie's point about modern roses not going into dormancy is obviously correct. Unlike woody perennials like Rhododendron or lilacs, roses apparently do not have a dormancy "chilling requirement"  in order to generate next season's bloom cycle. Rather, as Gary says, modern roses, as remontant, repeat-blooming  plants, "by their very nature, fail to go dormant in winter. So they have a much-reduced ability to cold harden."  In other words, rose canes die back in winter because they do not sufficiently "cold harden" and this die-back can only be controlled at the crown or bud union levels by proper winter-protection, as described above.  This affirms something that I have advocated for many years, i.e., repeated applications of potassium in the fall to "cold-harden" rose canes before the first hard freeze. My experience, over more than 20 years, is that hardening rose canes off with a potassium feast has the effect of significantly reducing cane die back in the winter.  Please see my several articles about the "potassium feast":
http://jack-rosarian.blogspot.com/2012/08/potassium-special-k-ration-feast-for.html

http://jack-rosarian.blogspot.com/2013/10/rose-potassium-feast-application-6.html


But something else seems to be happening here


Over the last several years, as the Twin Cities metro has moved solidly into zone 5, my observations indicate that modern roses may exhibit a characteristic, which may be related to the chilling requirement inherent in plants that experience dormancy in winter.

Even though our winters are warmer, in terms of extreme minimum temperatures (EMT), they seem to be just as long, or perhaps even longer in certain years, thereby keeping our roses frozen for a longer period of time. For example, our ground (and therefore our roses) stayed frozen into late April or early May in 2013, and we had snow on the ground into early May.  This is 2-4 weeks later than normal. What happened in May, once the ground thawed out, was that the roses had a very hard time getting started and there seemed to be more die-back than usual, even with shrubs that are zone 3 and 4 hardy. One of our husband-wife TCRC members,who have had good success over the years planting their hybrid tea and shrub roses with bud-unions and root crowns six inches below ground level, and using minimal winter protection above ground, lost a number of roses in 2013, even though the same method had worked perfectly in colder EMT winters.

In other words, with a 2013 EMT of -13 (well above the median for zone 5), our roses actually seemed like they had been through a much harder winter.  So it would appear that the length of time roses are frozen, not just the low temperature in a given year, impacts survivability.  After all, if you think about it, frozen is frozen; the only thing that happens with a lower temperature is that the ground freezes deeper and the roses take longer to thaw out and start growing in the new season.  But what happens to them when the winter is so long that they can't start growing again in a timely way?  To my knowledge there is no scientific reasoning for this phenomenon.  However, I found a clue in Part III of Gary Ritchie's series, where he speaks of cold weather breaking dormancy in plants.  Speaking of dormant plants in the first person, he says:

 "...One way would be somehow to keep track of the amount of cold weather to which you had been exposed during winter.  After a certain number of hours or days of cold exposure had occurred you would have a clear indication that winter was finally over and it was safe to resume growth.  This is exactly what plants do...."

What he is saying is that dormant plants apparently have an internal clock mechanism buried deep in their DNA that tells them it's time to start growing again, after they have been exposed to a certain number of hours or days of cold weather.  However, what happens if that internal clock tells them it's time to grow and they're still frozen solid?

Now, this is pure conjecture on my part but, based on my observations in the past year, I would theorize that (1) modern roses, although they do not experience dormancy, might share a similar DNA clock mechanism with plants that do, such as their first-cousins, the species roses; and (2) the growth signal coming from within the plant might be distorted by longer than historically normal periods of remaining frozen, such that the plant's internal growth pattern is interrupted, or even curtailed altogether, thereby causing much slower growth or even plant death.  This could account for what I and a number of Minnesota friends experienced in our warmer, but longer than normal, winter of 2013.  This was truly something I had never seen in my near-lifetime of growing roses in zones 4, 5 and 6.

I had been thinking about this since last spring and Gary Ritchie's four-part series in the American Rose was such an “a-ha” moment for me, that I couldn't wait for the next installment to come.  Gary might not agree, but it seems logical to me that, while modern (non-species) roses do not experience dormancy, per se, they might share some form of the so called "chilling requirement" of species roses.  There is much we don't know about the effects of winter on roses but, by observing the effects of the weather anomalies we are currently experiencing, we can learn a lot about what makes our roses tick and how we can better protect them in winter.  Unfortunately, we can't do much about the undue length of some winters, except to realize that not all winter effects on roses are related to extreme low temperatures.

I would be very interested in the reactions of readers to the theories I have set forth in this article.  My findings are 100% empirical and can be enhanced by the observations of others growing roses in cold zones. As always, please let me know what you think.

Jack Falker
jack@falkerinvestments.com
December 27, 2013

Note:  Dr. Gary Ritchie's four articles on Dormancy appeared in the May/June, July/August, and September/October, 2013, and the January/February 2014 issues of the American Rose.  By the way, articles like these, written by outstanding rose-scientists like Gary Ritchie, are one more reason that all rosarians should be members of the American Rose Society!