The Pesticide-Free Rose Garden

Author's note: This is the most important blog I have written.  I am advocating a new way of growing roses; contradicting the conventional wisdom set forth in virtually every rose book of the last century, including, most recently, the "2015 American Rose Annual". 

I have received excellent encouragement and advice, over the last two years, from Applied Bio-nomics in British Columbia, Rincon-Vitova Insectaries in California, and the IPM director of Butchart Gardens in British Columbia.

I know there are others trying to do what I advocate with varying degrees of success but, to my knowledge, there is nothing in the rose literature that provides instructions on how to grow roses organically, with beneficial insects and predatory mites completely taking the place of pesticides.

It is my intention to change the way roses are grown.  This is not a perfect process and it requires patience to let nature take her own course, given what we've all had drilled into our heads about pesticides.  But I can say conclusively that growing roses organically works, based on my experience of the last two years, plus the growing body of evidence from organic farming practices globally.

Please join me in this adventure.  You will be pleasantly surprised and rewarded for your efforts and patience.  I will be writing about this often and I encourage your questions and observations.

The Pesticide Culture

I grew up in a rose garden; beautiful and full of pesticides.  I remember the acrid smell, as my dad "dusted" his roses with fungicides and insecticides. And, of course, that meant we were all breathing the poisonous dust.  Making matters worse, ours was just one of three neighborhood rose gardens, within less than 100 feet of each other in Detroit, and everyone was doing the same thing.  My dad even had a crank duster that spewed out the pesticides, and he wore no protection. Here's a picture of F.F. Rockwell, author of "The Rockwell Complete Book of Roses", dated 1963, which has been one of my rose "bibles", showing us how to do exactly what my dad did in the 1940s and '50s, with no protection but his hat and his pipe! (Note the cloud of dust right in front of his face.)

I have a collection of rose books, some of which date back to the 1930s and 40s, and they all say virtually the same thing about the need for pesticides.  Here's what McFarland and Pyle said in their 1937 classic, "How to Grow Roses": 

"There is only one cure for insects which eat the flowers and leaves; that is to poison them.  It is, therefore, necessary that the poison be on the leaves before the insect starts to chew.  Since there is no way of knowing when an insect wants to dine on a rose leaf, the only way to prepare for him is to keep poison on the plant all the time." 

Notice they don't recognize that there may be good bugs and bad bugs; just kill them all. But what about all the butterflies, lace wings, lady beetles and the hundreds of different varieties of pollinating bees and wasps?

Lest you believe that anything has changed in the nearly 80 years since that book was written, please note that the only article devoted to rose care in the 2015 American Rose Annual (which is essentially a pretty travelogue of rose gardens) is "How to Improve Performance of Pesticides: Timing, Coverage and Frequency". Plus, at the beginning of the Annual, the American Rose Society endorses seven pesticides. Here are excerpts from that pesticide article (by a Ph.D no less):

"Pesticides such as insecticides, miticides and fungicides are commonly applied by rosarians to control insect and mite pests and diseases.  In fact, roses require extensive inputs from pesticides in order to maintain the aesthetic quality of both the foliage and flowers.... Examples of systemic insecticides that may be used on roses include acephate (Orthene), imidacloprid (Merit) and thiamethoxam (Flagship)...." (Emphasis mine)

So nothing has changed. In fact, things may have gotten worse. Here we have an article in the "2015 American Rose Annual" telling you to spray Orthene, an organophosphate, which is one of the most dangerous insecticides on the market (i.e. it kills everything that touches it, like bees, butterflies, lacewings, lady beetles etc.), and imidacloprid, the Bayer neonicotinoid, which is strongly implicated in bee colony collapse disorder and is already banned in several countries.

What's happening here is that we, as rosarians, have been consistently told that all insects are bad and must be killed, in order to grow beautiful roses.  Nothing could be further from the truth!

Spray Nothing!

I finally realized, after many years of spraying all of the above, including  Orthene, imidacloprid and pyrethroids like Demand CS (which is what I thought I was supposed to do to control everything from aphids to Japanese beetles), that what I was really doing was wiping out every naturally occurring beneficial and predator insect in my garden, not to mention pollinators like bees and wasps .  For example, I suddenly realized that I no longer saw lady beetles and lacewings, which are natural predators for spider mites.  It's no wonder because, instead of tediously picking Japanese beetles off my plants and drowning them in soapy water, I sprayed them with Demand CS, which works really well, but also wipes out all other beetles (like lady bugs), as well as every other predatory insect in the garden.  As a result, I ended up with a massive infestation of aphids (something I hadn't seen in years) because I had destroyed all their predators, in my efforts to deter Japanese beetles.

About two years ago, my compatriot-rosarian friend Paul Zimmerman mentioned a new book by Jessica Walliser, "Attracting Beneficial Bugs to your Garden", which changed my way of thinking about controlling insect pests in my gardens.  Here's a link to that book, which is available in many public libraries, as well as both new and used on Amazon:
http://www.amazon.com/Attracting-Beneficial-Bugs-Your-Garden/dp/1604693886/ref=sr_1_1?ie=UTF8&qid=1417916500&sr=8-1&keywords=attracting+beneficial+bugs+to+your+garden

What Jessica advocates is the establishment of "insectary gardens" to attract beneficial insects (good bugs), such as syrphid flies, lady beetles, minute pirate bugs, lace wings and predatory wasps that attack "bad bugs" such as spider mites, thrips and aphids. As long as you don't spray things that kill them, these predators are very easy to attract to the garden with plantings, such as oregano, dill, bachelor buttons, lobelia, yarrow, daisies, alyssum and cosmos (and many others cited in the book).

The Two-Step Process for Pesticide-free Roses

Please note that these steps should be accomplished almost simultaneously, with predatory mites being introduced in warm weather, right after insectary gardens have been planted.

Insectaries

To get started, I found several areas in my yard that could be converted to insectaries.  My first was a sizable spot where we had previously grown raspberries; my second was a new garden that I planted for the first time in 2015. Then, I opened up small areas in each of my rose gardens for insectary plantings. In one case, I removed several roses and replaced them with insectary plants. Here's how that little garden segment looked in 2014, with oregano, bachelor buttons, cosmos, dill, yarrow and a few other things to attract beneficials (Buck's Prairie Harvest is to the right). When I took this picture, the insectary was teeming with wasps, bees and other beneficial insects that were nowhere to be found in my gardens the previous year:



Below is the insectary garden that replaced my raspberry patch.  Note the mating Monarchs on the lobelia; a great example of what happens in an insectary garden.

Below is my new insectary bed, which was planted in 2015;
complete with an Eastern Black Swallowtail.

And Here is a picture of an Angelica plant in action in the "raspberry" insectary, in 2015.  This one attracts large numbers of parasitic wasps, minute pirate bugs, lady beetles, syrphid flies and tachinid flies; all very important beneficials in the fight against spider mites, thrips, aphids etc.  Note that there were at least three wasp varieties on the plant when this picture was taken.

I should also note that, because oregano attracts so many beneficial insects, I have planted a little patch of it, right in the middle of each of my rose gardens.  Of course it spreads quickly, so I have to chop it back and transplant pieces elsewhere in the garden, each spring.  When it blooms, it is literally covered with beneficials, which, of course find their way onto every rose plant and bloom.

And here is the old Minnesota Rose Gardener showing off one of my insectaries, with zinnias, lobelia and cleome. I find that I am never happier than when I am in the garden, among the bees, wasps, butterflies, and other pollinators and beneficials.

Patience

One of the most important things Jessica Walliser talks about in her book is the importance of patience.  When there is an infestation of insects like aphids, thrips or spider mites, it takes time to build up enough predatory mites and beneficial insects to feed on them. In the meantime, while being patient, use the first line of defense for aphids and spider mites, which is washing the bugs off with water. I have learned that spider mites succomb to a fine mist of water, thereby not washing off beneficial mites with a sharp stream of water. Thrips are harder to deal with, so the first line of defense is always to pick and dispose of affected blooms in such a way (as in a covered can) that the thrips can't fly back into the garden.  Here is the kind of thrips-infected bloom that should always be immediately removed.

For Japanese Beetles, pick or shake them off into a can of soapy water (more on this later).  But by no means should you give in to the temptation to spray an insecticide, because that will ruin the entire process underway in your garden. In short, just remember that predatory mites and insectaries really work, if you give them a little time! And Japanese Beetles must be handled seperately.

Predatory Mites

The several varieties of these tiny arachnids are very efficient predators for pests such as two-spotted spider mites, eriophyid mites and thrips.

Stratiolaelaps (Ss) should be the first mite to be introduced in rose gardens.  It is a generalist soil predator that feeds on pupating thrips and overwintering spider mites.  It is also known to feed on pupating rose midge, but it it has not yet been proven as a control, and several midge trials are underway.  It has been very effective on thrips in my gardens, in just one year, and it is known to overwinter in both Canada and the United States.  Here is a good description and video from Applied Bio-nomics, in Victoria, British Columbia:
http://www.appliedbio-nomics.com/products/stratiolaelaps/

And here's what Ss looks like in the soil:

Cucumeris feed on thrips larvae. They sense thrips emerging from leaf tissue and wait to bite the heads off the emerging thrips. However, Cucumeris is a true generalist, capable of providing preventive control against the Two-spotted Spider Mite, and also an effective Biocontrol for Broad and Straw Mites. It also eats whitefly eggs. It does not overwinter in northern climates and must be re-introduced each year. Here is Applied Bio-nomics' description and video:
http://www.appliedbio-nomics.com/products/cucumeris/

And here is a really good picture of Cucumeris feeding on Thrips:

Fallacis is the most effective preventer of spider mites available. Applied Bio-nomics hasn't found a mite that Fallacis wont control.  This is very important because, in my garden I found (with the help of Applied Bio-nomics) that I was fighting both Two-spotted Spider Mites, plus some type of Eriophyid mite; most likely the "Broad" mite. Some Eriophyid mites carry Rose Rosette disease (fortunately not the one I've been fighting) and this makes the presence of Fallacis all the more significant in rose gardens.  Fallacis overwinters everywhere in the continental United States and as far north as northern Quebec in Canada.  Here is Applied Bio-nomics' video description of Fallacis:
http://www.appliedbio-nomics.com/products/fallacis/

And here is a picture of Fallacis at work feeding on a Citrus Red Mite:

Here is a picture of Earth Song in my garden, showing damage by Eriophyid mites, which I mistook for Spider Mite damage.  Fortunately, Fallacis had a big impact on this mite in my gardens last summer.

Persimilis targets Two-spotted Spider Mites and is one of the oldest and best beneficials in use.  It is capable of complete eradication of its prey.  Like Cucumeris, it does not overwinter but, in all likelihood, if you use it in combination with Fallacis, you will not need to reapply it the following year, since spider mites should be under continuing control with overwintering Fallacis.  Here is Applied Bio-nomics description and video:

.http://www.appliedbio-nomics.com/products/persimilis-max/

And here is a picture of Persimilis at work:

Summarizing, Stratiolaelaps (Ss) is basic to contolling thrips and spider mites and should be introduced first, in the spring warmup.  It should only have to introduced once, as it should stay in the soil for many years.  Next, if Spider or Eriophyid mites are present, Fallacis should be introduced, to overwinter in the garden with Ss.  If Thrips are present, Cucumeris should be introduced in warm weather, as both a Thrips and Spider Mite control.  Finally, if Spider Mites have been a recurring problem, as they were for me, Persimilis can be added.  Remember that neither Cucumeris or Persimilis overwinter, so, if needed, they must be introduced again the following growing season.  In my own case, Thrips were a persistent problem until late in 2015.  In the event I see them again in 2016, I will immediately introduce Cucumeris for another growing season.

Sourcing Predatory Mites

The distributor for Applied Bio-nomics mites, that I have used, is Rincon-Vitova Insectaries in Southern California.  http://www.rinconvitova.com/

Rincon's pricing on Applied Bio-nomics' products is quite reasonable; however, product pricing is overshadowed by the cost of necessary overnight shipping. This can be mitigated by combining orders, as much as possible.  For example, if you are ordering product in late spring or early summer, Sratiolaelaps, Fallacis and Cucumeris can be ordered at the same time to save on shipping.  This should be discussed specifically with Rincon.

I have always taken into consideration the high cost of miticides and insecticides and recognized that I am ultimately eliminating them with predatory mites and beneficial insects.  Based on my experience of the last two years, I believe it's well worth the up-front cost of predatory mites and any other beneficial insects you might choose to import.

My primary contacts at Rincon-Vitova have been Gabriel or Kyra at 800 248-2847. They will be expecting calls from rosarians.

Here is a list of Applied Bio-nomics distributors, worldwide:
http://www.appliedbio-nomics.com/distributor-map/ .

Japanese Beetles

I believe the most viable way of dealing with Japanese Beetles (JBs) is knocking them off the plants into soapy water, i.e. without insecticides.  Unless you are running a very large public or commercial garden and have no other alternative, the repeated use of insecticides on JBs is just too devastating to everything else in the garden.  Here is an excerpt from the 2015 revision of my JB blog post:

After several years of experimenting with insecticide control of JBs, I am firmly convinced that it is the wrong approach in the home or small public garden for the simple reason that it massacres all other beetles in the garden, most notably the lady beetle, which is perhaps the most important beneficial bug for controlling a variety of insect garden pests.  Also, all of these insecticides harm pollinators, especially bees, as well as virtually all other beneficials such as wasps, syrphid flies, lacewings, minute pirate bugs etc., as well as predatory mites, which attack a large variety of pests such as aphids, thrips and two-spotted spider mites.  Once I began controlling JBs with insecticides, many of my bees disappeared and I experienced an infestation of all the pests listed above; a lesson well learned!  It has taken me two years to re-establish beneficial bugs in my gardens and I will never again spray insecticides to control JBs. 

And here is the entire text of that 2015 JB blog post:
http://theminnesotarosegardener.blogspot.com/2015/07/the-beetles-are-coming-beetles-are.html

Fungicides

Generally, fungicides and the spreader/stickers that accompany them do not completely devastate beneficial insects or predatory mites, although it is obviously better to not use anything toxic.  However, my experience is that it is virtually impossible to eliminate fungicides altogether in the rose garden, even though planting roses that are resistant to the blackspot fungus (e.g. Earth-Kind and Buck roses) goes a long way toward minimizing the necessity of spraying.  Also, if you must spray, it's very important to spray the right fungicide, i.e. one that kills blackspot spores, rather than simply deterring them.  Only one fungicide, Manzate/Mancozeb, is known to actually kill blackspot spores, so using it minimizes the need for repeated spraying.

Here is my 2012 blog "There's a Fungusamongus!" that deals extensively with this subject:
http://theminnesotarosegardener.blogspot.com/2012/07/theres-fungusamongus.html


Here is a partial list of the beneficial insects we all want in our gardens:

• Bees of all varieties (there are more than 400 bee species in Minnesota).
• Predatory Beetles, especially Lady Beetles
• Syrphid Flies
• Minute Pirate Bugs
• Lace Wings
• Predatory Wasps
• Butterflies

And here is a list of some of the plants that attract beneficial insects:

• Oregano (I have a little patch in the middle of every rose bed)
• Dill
• Angelica
• Lovage
• Daisies
• Yellow Cone Flowers
• Sunflowers (both annual and perennial)
• Bachelor Buttons
• Alyssum (On the edge of every rose bed to attract Syrphid Flies)
• Verbena Bonariensis
• Zinnias
• Boneset
• Cosmos
• Coreopsis 
• Monarda
• Rudbeckia (Black-eyed Susans)
• Aster
• Yarrow
• Anice Hysop

An excellent mail-order source for some of the less common plants listed above and in Jessica Walliser's book is Prairie Moon Nursery in Winona, Minnesota.
https://www.prairiemoon.com/

Please send me your comments and questions.

Jack Falker
@mnrosegardener
jfalkersr@gmail.com

May 2016

When to Uncover Your Roses (Or Not)

If you live in the Upper Midwest, the simple answer is not yet!  Here in Minneapolis/St. Paul, we have had a very light winter, courtesy, first, of our well-documented climate-change, which is literally the most extreme in the United States; and second, the ubiquitous El Nino, which made our winter even milder (all the heavy winter weather went south and east).  Our extreme minimum temperatures (EMT) this winter occurred on January 17th (-14 f) and 18th, (-13 f), just above the midpoint of USDA zone 5.  All of our other night-time lows were in zone 6 or warmer. So, if you live in the Twin Cities and you heavily protected your roses for a zone 4 winter (i.e. the Minnesota Tip), it was sheer overkill, as predicted in my December 11, 2015, Minnesota Rose Gardener blog: "What's Happening to Winter?"

http://theminnesotarosegardener.blogspot.com/2015/12/whats-happening-to-winter.html

Even if you live in the outer-ring suburbs of the Twin Cities, or some of the towns in more-rural, southern Minnesota, you would have only barely touched zone 4 this winter. For example, Rochester, MN had an EMT of -21 F on January 18th.  All other EMTs were zone 5 or warmer.  Covering your roses by mounding and leaf bags, as discussed below, is ample protection for these low temperatures, as long as your hybrid-tea bud unions are planted correctly, i.e. below ground-level.

Nonetheless, getting back to my thesis, it is still far too early to uncover your roses, regardless how warm our weather in March might be.  Looking ahead in the 16-day weather model, it is expected that the low temperature on March 21st will be in the low 20s; too cold for newly uncovered, tender canes.  As emphasized below, it's freezing and thawing that kills roses, not simply freezing. And keeping your roses covered in warming weather will not harm them in any way. So, before you make the decision to uncover, be sure and check the long-range, night-time lows.  Yahoo weather is one of the most reliable sources for a ten-day forecast at your exact location, anywhere in the country.  Paul Douglas' weather blog is also an excellent resource for the long-range Twin Cities' forecast. Note his discussion of a distinct cooling trend in late March:

pauldouglasweather.blogspot.com

And here is a replay of last year's April 1, 2015, blog:

Uncovering Your Roses and When to Prune

When to uncover your roses in the Spring is really quite easy to determine, if you remember the reason for covering them in the first place.  That is, to keep them from freezing and thawing repeatedly over the winter months, which is what kills them.  In the Upper Midwest, where I live, we finish covering our roses at the point when the ground freezes and it is our objective to keep them frozen all winter.  Let me repeat that: In the Upper Midwest, we don't cover our roses to stop them from freezing; we cover them to keep them frozen.  Every method of winter protection in this climate, including the Minnesota Tip, has that same objective, and I am always surprised when people don't understand that.  Our ground freezes generally at least two feet down and sometimes, as in the winter of 2013-14, it freezes down as much as four feet.  So it shouldn't be hard to understand that everything planted at the surface freezes, regardless of how you insulate.

For folks in warmer areas, like the warmer parts of zone 6 and throughout zone 7, where the ground freezes down a few inches and then repeatedly thaws and refreezes throughout the winter, the purpose of winter cover would be the same, i.e. to keep the roses from repeatedly freezing and thawing, but in this case it would be to insulate them to prevent them from freezing in the first place.  It really amounts to the same thing,  however.

Given these principles, when to uncover your roses should be obvious, wherever you live.  It is simply when the danger of freezing and thawing has passed.  Around here, that usually occurs sometime in the first two weeks of April but virtually never in March, regardless how warm it might get for a few days.  Let me give you a recent example.  In the spring of 2012 we had 70 and 80 degree weather in mid-March causing fruit trees to blossom etc., but in the next week we had 10 degree weather followed by at least two weeks of below freezing weather.  This caused the loss of almost the entire apple crop in Minnesota and Wisconsin and virtually the entire cherry crop in western Michigan.  If you had uncovered your roses in March 2012, thereby allowing them to thaw out, you would have suffered severe damage when they froze again.

I realize that it is very tempting to uncover your roses when it first warms up in the spring.  If you use the leaf bag method, which I have advocated in my blogs, you can choose to partially uncover your roses by rolling the leaf bags back but leaving them ready to replace, if the weather turns cold again.  This approach allows the plants to begin thawing and to soak up spring rains, while keeping your options open for easy recovering.  I would say that I use some form of this approach almost every year, especially when it starts to rain (vs snow!).

Today, April 1st, it was 82 degrees and we are expecting thunderstorms tonight so I decided to go out and roll the bags off my roses, while keeping them close-by, if I have to roll them back

Wherever you live, my suggestion is to watch the seven-day weather forecasts in early April and try to determine when your nights stay consistently above 25 F (-4 C).  If you keep the mounds around your plants, even if you pull the bags back, temps down to 25 F will not refreeze your plants.  If you are in doubt, just keep your plants covered until mid-April, around here.  It won't hurt them.

And here's a quote from Paul Douglas' weather blog (on April 1, 2015):

"Another Relapse After a May-like temperature swoon today temperatures cool off later this week, a taste of early March shaping up for early next week with readings struggling to reach 40F Monday and Tuesday. European guidance is even hinting at a rain/snow mix, especially north of the Twin Cities. Don't rule out more slush before the daffodils arrive."

On the theory that a picture is worth a thousand words, here is how my beds look after rolling back the leaf bags this afternoon.  Note that the roses still have plenty of leaves and mulch around them and the bags are right there if I want to roll them back over the plants. Incidentally, most of those leaves around the plants will get pushed back in the bags and be transported to my compost pile, when it's time to finally uncover the beds, which will probably be in 10 to 14 days, when Paul Douglas is no longer warning about slush and freezing temps.

Pruning
I always laugh when I hear someone say you should prune your roses when the forsythia blooms. Suppose it had bloomed in mid-March 2012, as mentioned above, when your roses were still covered?  When the forsythia blooms really has nothing to do with when you should prune your roses. Pruning for me is a two step process.  First, right after I uncover my roses (i.e. mid-April), I begin by cutting off all the dead wood, right down to where the canes begin turning green.  This is a very rough, quick cut that I do with my battery-powered Black & Decker hedge trimmer.  I don' t worry about rough cuts on the canes because I know I'm coming back later to make my final pruning and shaping cut.  All I want to do is to take off the "overhead" of dead wood to clear the way for new growth that will come from the green canes.  Once I can see that nodes on the green canes are starting to swell, in anticipation of setting new leaves, then I begin my second cuts to shape the plants and eliminate any weak, wispy growth from last year.

So, in summary, you should first cut off all the "overhead" dead wood and then, when the plants show signs of growing, make your second cut and seal it off to stop saw-fly wasps from burrowing into the fresh wood to lay eggs.  I use Elmer's school glue for my sealant, which works very well and is quite inexpensive.  And the forsythia may or may not have bloomed when you finish.  We're talking roses here, not flowering shrubs!

Jack Falker
April 1, 2015

What's Happening to Winter?

The United States has just experienced its warmest autumn in history. In Minneapolis-St. Paul, temperatures in December are running about 20 degrees (f) above average; an average already pulled much warmer over 50-plus years. December in the Twin Cities is when our miriad of shallow ponds freeze, with our deeper lakes not far behind.  Not this year; what ice had accumulated has all but disappeared and what would normally be a deepening snow pack is all in the form of rain or slush.  Golf courses are open and my greening lawn looks like it could use a cutting.  And we're expecting up to an inch of rain over the weekend (which would be a foot or more of snow, if it were about five degrees colder)!

In his December 12th weather blog, my friend Paul Douglas, founder of Aeris Weather and WeatherNation says:  "... What makes our current stretch of (irrational) warmth unusual is the sheer persistence of the mild signal: day after day, week after week, month after month.... Since September 1, over 80 percent of the days have been warmer than average, according to (Minnesota state climatologist) Mark Seeley. Further, if you add in the first 10 days of December, the stretch of days from September 1, 2015 to December 10th is the warmest in state history, a remarkable run of warmth."

And here is a Climate Central map that Paul published:



Here is the address of Paul's weather blog, in case you would like to read more: http://pauldouglasweather.blogspot.com/

Something is going on here.  It looks like we could have a St. Louis winter (USDA Zone 7) in the Twin Cities (i.e. not below zero). And in St. Louis?  How about an Atlanta winter, and so on.  For the last several years, I have been developing and analyzing extreme minimum temperature trend lines, extending over the last 55 years, for Midwest cities, and my conclusion has been that the upper Midwest is warming faster than any other area of the country and that winters would become warmer still over the next several years.  I just didn't think it would happen quite this soon.

As a long-time, cold-zone rose gardener, I have been lightening up on my winter protection a little each year.  This year, anticipating a massive, climate-change-driven El Nino, I decided to use only compost-mounding, with no insulating leaves; a process that I might have used in Detroit (Zone 6), 40 years ago.  For several years, I have been writing that using the Minnesota-Tip winter protection procedure in the Twin Cities is a lot of unnecessary hard work and a horiticulturally unsound practice, given the trend of our winters (see my blog: "No Tipping Please").
http://theminnesotarosegardener.blogspot.com/2012/08/no-tipping-please.html

What surprises (and amuses) me is how many people around the Twin Cities still tip their roses.  Even the University of Minnesota Landscape Arboretum still tips their roses (courtesy of the strong backs of the Minnesota Rose Society).  The reason for this, I believe, is that, in order to effectively use the "tip" method, the bud unions of hybrid tea roses must be grown at or above ground level, which, in itself, is a horticulturally unsound practice (wherever you live). So, in order to get out from under the "tip" method, you have to re-plant your bud unions deeper, which is a simple, one-time procedure (I know, I did it).  Also, old habits (and fears) die hard, but people just need to stop and recognize what's happening around them, and trust the statistical evidence.

I am also amused by articles written in local rose newsletters this past year referring to our brutally cold Zone 4 winters.  The extreme minimum temperature last winter (2014-15) was -11, only one degree shy of being in Zone 6.  Our coldest winter in many years, 2013-14 (with the horrible polar-vortex effect) had only one night falling a few degrees into Zone 4, at -23. All other night-time temps were Zone 5 or Zone 6. People who dispute these facts are probably thinking about wind chills, which have nothing whatsoever to do with plants.  See my blog "Don't Sweat the Wind Chill":
http://theminnesotarosegardener.blogspot.com/2015/01/dont-sweat-wind-chill-on-your-roses.html

The Statistical Facts

The mathematical study of statistics focuses on the probabilities that certain events will happen (or not).  Put another way, statistical analysis can be predictive.  So, when we perform valid statistical analysis on regional winter weather, over many years, and we can see very clear trends developing, we are positioned to make predictions about future winters.  As cold-climate rose gardeners, this is pretty important because it allows us to make informed decisions about which roses to plant and how to winter-protect them most effectively.

For several years now, I have been doing 50-plus year statistical analysis on Minneapolis-St. Paul winters and comparing them with winters in other upper-Midwest cities.  The results are pretty amazing in that we can see very distinct warming trends developing. And it has become much easier to predict that these trends will continue and that we will see warmer winters going forward.  The meteorological winter of 2015-16 began on December 1st and what we are now seeing is exactly what the trend line shows we should expect: temperatures are much warmer than average, an average which itself has been pulled significantly upward over the last 55 years.  Below is my chart for the 55 winters beginning in 1961, through 2015, in the Twin Cities. What it shows is that since year 2000, all but three of our winters have been in USDA Zone 5 or higher, even though the USDA continues to rate MSP as Zone 4 (based on data that is now 10 years old).  What's most important here is the upward slope of the trend-line, which, as mentioned above, is predictive.  What the trend-line shows, if you extend it, is that MSP will be firmly in Zone 6 within the next three or four years.  Right now, based on what we are seeing, I believe we will see a Zone 6 winter in 2016, for the second time in history, and there is a distinct possibility that it could be Zone 7, i.e. not below zero at all, which would be a first.

Below is the 55 year trend line for Chicago.  Note that while Chicago has moved firmly into Zone 6, the slope of the trend line is shallower than the MSP line. In other words, while Chicago is warming, it is warming more slowly than MSP.  Interesting that Chicago's 2015 low temperature was -10, right at the      lower edge of Zone 6, while MSP's low was -11, right at the upper edge of  Zone 5; virtually no difference.



And below is the 55 year EMT trend line for St. Louis to give us some idea of what a Zone 7 winter might look like.

The differing slope of these trend lines is born out in Climate Central's chart below.  Note that the MSP area and points north along the Minnesota/Wisconsin border, as well as the Red River Valley in Northwestern Minnesota, have warmed more than any other area in the country.



Finally, let's look at NOAA's Winter Outlook for 2015-2016 and note that most of Minnesota is projected to be 50-60% warmer than average this winter. In the short term, this is attributed to El Nino ("the child"), but it is important to recognize that the phenomenon of El Nino is itself the "child" of long-term climate change. In other words, it is becoming impossible to differentiate short-term from long-term effects.  If you go back and look at all of these graphs and charts together, there is a great deal of similarity in the pace of warming in the northern tier of states.  And this is exactly what the trend lines above are pointing toward.



There is growing evidence that, with the extreme warming of the oceans, El Nino could become a long-term phenomenon.  Here is another snippet from Paul Douglas' weather blog, quoting a climatologist at NASA's Jet Propulsion Laboratory:

"Monster" El Nino Could Usher In Decade of More and Stronger Events. A sign of things to come?  "...While El Nino oscillates on a more or less yearly cycle, another dynamic in Pacific Ocean water temperatures, known as the Pacific Decadal Oscillation (PDO), has the potential to accelerate global warming and increase the severity of El Nino episodes, scientists said. The last time the PDO was, as it may be now, in a prolonged positive, or "warm" phase, it corresponded with two of the strongest El Ninos on record. "When you really have a monster El Nino, it could be enough to flip the PDO into a new phase for a decade or so," said William Patzert, a climatologist at NASA's Jet Propulsion Laboratory in California. "Keep your eyeballs peeled because maybe we're in for a decadal shift..." 

While this may be good news for rose gardeners, it is very bad news for our planet.  In the meantime, my advice to upper-Midwest gardeners is to plant your bud unions a couple of inches below ground and forget about uprooting and tipping your roses.  For northern-gardeners, like myself, who keep our roses firmly planted and mounded in the winter, it may be time to lighten up a little, but winter cover will still be important.  It still gets cold in Zone 6 and freezing and thawing (the roses' winter enemy) is an even bigger problem in a warmer winter environment.

Jack Falker
@mnrosegardener
jfalkersr@gmail.com
December 12, 2015

Protecting Roses from Vole Damage

Right now, as the ground freezes, is the perfect time to protect your roses from vole damage during the coming winter.  The correct approach is two-pronged: First, voles are deterred by castor oil applied to the ground in areas where they burrow, so applying castor oil, in the right dilution as winter sets in, should be your first line of defense.  Next, the strategic placement of vole baits to kill those varmints that might make their way through your castor oil deterrent is your second line of defense.

Today (November 13th), I made my application of castor oil, which I buy inexpensively from Wal-Mart in their health and beauty area. It is also available from several vendors on line, if you do not have access to a Wal-Mart store. Please note that it is important to mix castor oil with liquid detergent as you dilute it with water in the proportions given below.  The soap helps the oil dissolve in the cold water so that it doesn't stick to your sprinkling can.  I inadvertently mixed some once, without the soap, and it gets very sticky and messy.

I discuss this two-pronged approach very thoroughly, plus much more, in my October 2012 blog post: "Voles". Here is the address of that blog:
http://theminnesotarosegardener.blogspot.com/2012/10/voles-and-roses.html

And here are a couple of excerpts from that blog post:

Castor Oil: This is the most effective solution I have found.  Voles really don't like castor oil; apparently, from what I have read, it makes them sick, and they avoid an area on which it has been applied.  Mix one or two teaspoons of castor oil (I use more rather than less) and one teaspoon of liquid detergent, per gallon of water, and apply it liberally around the bases of your roses and generally around your rose beds, where the voles might travel/burrow in the winter.  The best time to do this is in late Fall, when the ground is lightly frozen, just before putting your final mulch or leaf cover around your roses. Around here, that would be in mid to late-November.  I mix it in a 30-gallon trash container, pump it out with a sump pump, and apply it with a hose and watering wand, exactly like I do liquid fertilizers and potassium. You can also use a sprinkling can to apply it, if your garden isn't too big.

Note: Two teaspoons of castor oil per gallon in 30 gallons of water amounts to 10 ounces of castor oil.  Wal-Mart's castor oil comes in 6 ounce bottles, so it takes a little more than 1 1/2 bottles for a 30 gallon trash can of the oil/soap/water mixture.  A friend in Wisconsin reports that he is using one tablespoon (3 TSP) of castor oil and one tablespoon of soap per gallon and that's just fine.  In this case, more is better to deter these little monsters.  In fact, in 2017, I just used 2-bottles (12 oz.) of castor oil and 30 TBP of dish soap per 30 gallon can, just to keep it simple.  This should give you some idea of how much to buy.

Pour the castor oil and soap into the 30 gallon can and then add water, stirring while you go.  I also think it goes on just as easy with a sprinkling can as it does with a pump, so that's what I'm using now.

Rodent Baits:  Killing voles is desirable, before they over-run you, but this is a touchy subject because rodent baits can also affect other animals, like neighborhood cats and dogs.  The common rodent bait that you find in most stores is an anti-coagulant poison, which, when eaten a couple of times, stays in the intestines, causes massive internal bleeding and kills the animal.  I used it in my rose beds for years, without thinking, until about five years ago when we got a new kitten and he managed to find a mouse or vole that had eaten it, in among the winter-protected roses.  I will save you the terrible details, but it resulted in a very large emergency veterinary bill.... After that experience, I went to work researching what other non-coagulant rodent baits might be on the market, and I found one.  The brand name is "Eraze", made by Motomco, the same company that makes the anti-coagulant baits.  The active ingredient in this one is Zinc Phosphide, which is nonetheless a poison, but acts in a different way, killing small animals immediately after ingestion.  There are conflicting opinions on this, but an article by Michigan State University indicates that it is less lethal to larger animals, such as cats and dogs, because their normal reaction after ingesting it would be to regurgitate it rather than digest it. 

I have written a couple of other articles about vole protection, which contain several other comments and ideas.  Here is my September 2013 post:
http://theminnesotarosegardener.blogspot.com/2013/09/voles-and-castor-oil.html

As always, please send your questions or comments to: jfalkersr@gmail.com .

Jack Falker
November 13, 2015

Winter-Protecting Your Roses

Here is an article I wrote for the October 2015 Twin Cities Rose Club Newsletter. While I reference Minnesota winter conditions, it is applicable anywhere in the upper-midwest and to virtually any kind of roses.  The key message is to prevent your roses from repeatedly freezing and thawing.  In a cold zone (3,4,5) that means keeping them frozen all winter.  

Winter-Protecting Your Roses

Jack Falker

@mnrosegardener

Everyone in Minnesota knows they have to do something to winter-protect their roses.  However, not everyone seems to know exactly what they’re supposed to accomplish and, thus, what the best method might be. So let’s start with the one basic principle that applies in all cold zones, i.e. USDA Zones 3, 4, 5 and parts of 6, and to virtually all types of roses, whether they be hybrid teas or shrubs; grafted or own-root.

Fact: The primary objective of winter protection in the cold zones is to keep your roses frozen, not to keep them from freezing.  There seems to be a lot of confusion about this and, unbelievably, we still have nurseries selling styrofoam rose cones, which serve as little ovens in the winter, when the sun shines on them, causing plants to freeze and thaw repeatedly, thereby killing them.

There are two basic ways of keeping roses frozen where we live: (1) the Minnesota Tip and (2) mounding with compost and insulating with leaves or hay.  Let’s be clear about the “tip” method:  When you tip your roses over in a trench, bury them in dirt and compost, and put leaves on top, they are definitely going to freeze solid in the ground, as the frost permeates down several inches. In fact, many Minnesota-tippers soak their tipped roses, before turning off their water for the winter, so they will be contained in blocks of ice.  In other words, the objective of the “tip” method is to freeze roses solid and keep them frozen until spring

I personally believe that keeping my roses standing upright and firmly planted, while mounding and insulating them, is the best way to winter-protect. I tipped my roses for many years but always felt that it was not horticulturally sound to partially uproot the plants and cover them with dirt in mid to late October, when many of them were still in bloom.  The longer I did it, the more my gardening instincts (not to mention my back) kept telling me I should be doing something different.  Take a look at my August 2012 Minnesota Rose Gardener blog post  "No Tipping Please”:

http://theminnesotarosegardener.blogspot.com/2012/08/no-tipping-please.html.

Many people, who have been tipping their roses for years, feel trapped in the procedure because the bud unions of their grafted hybrid teas are above the surface of the ground.  This is a basic problem, which is endemic to the tipping procedure.  For a variety of sound horticultural reasons, the bud unions of grafted roses and the crowns of own-root roses should not be above ground, regardless of where you live, warm or cold. My advice to these folks is: Instead of tipping your roses this year, dig them out entirely, taking a good root ball, heel them into a trench, a foot or so deep, and cover them with a good layer of dirt and mulch (to keep them frozen).  Then in the spring replant them in the same place, except this time plant them with the bud unions several inches below the surface.  If your garden is large, you might do this in stages, some this year, some next year etc.  Another alternative might be to raise the level of soil in your beds so that your bud unions are at least slightly below grade.

With your roses properly planted, here is what I recommend for winter protection.  First, in mid-September and for six successive weeks, give your roses a potassium feast to help their canes harden off, before the first hard freeze.  It’s too late to start the feast this year (I’m about to do my fourth application) but I believe potassium is important in winter protection.  For future reference, here is the address of my most recent blog on the potassium feast:

http://theminnesotarosegardener.blogspot.com/2015/09/its-time-to-put-potassium-on-your-roses.html

Next, gather any wood chips or other clean mulch in your beds and mound it around your plants.  Then, mound several shovels of compost around every plant, so that the plant crowns are thoroughly covered.  My compost is primarily shredded oak leaves from last fall and hundreds of pounds of composted Starbucks coffee grounds that I collect regularly. This compost is full of worms and worm castings, so it's just what the roses need in the spring, when I spread out the mounds and work the compost into the ground.  

Next, when it starts getting cold and your roses have stopped blooming, cut them down to about 12 inches and bind them into tight bundles. One other thing you might do, especially if you’ve had spider mites this summer, is to strip the leaves off the plants and spray them with horticultural oil. (Don't worry, you're not losing anything here; what you want is the strong new growth you’ll get in the spring.) 

The final step is to prepare enough half-full plastic leaf bags to cover each of your roses. (Don't use the new compostable bags; they break down over the winter and leave you with piles of leaves to clean up!)  Now, wait until the ground freezes and, with the objective of keeping your roses frozen, slit open the bottoms of your leaf bags and shove them down over each of your tightly bundled plants, flush with the mounds.

So, can you see how this approach will keep your roses frozen? When you start to carefully roll the bags off your roses in the spring (to keep as many of the leaves in the bags as possible for disposal or mulching), you will find that many of the bags are still frozen to the mounds and that your roses are encased in blocks of ice; exactly as you wanted them to be.  In fact, depending on how quickly it warms up, it may actually take longer for these mounds to thaw than roses that have been tipped. 

Regardless of how you choose to winter-protect your roses, please keep firmly in mind that your objective in the cold zones is to keep them frozen all winter. The other alternative, of course, would be to move to a warmer zone, where your objective would be the opposite, i.e. to keep your roses from freezing in the first place.  No such luck for me!

Jack Falker (@mnrosegardener)

10/01/2015

Time to Put Potassium on Your Roses

For those of us in the cold zones, i.e. USDA zones 3-6 (and maybe zone 7, given the vagaries of winter with recent polar vortex incursions), now is the time to begin feeding your roses a six week diet of potassium.  Here is a quote from my posting on this subject in September 2013.

"In the six weeks before the first hard freeze (i.e., down to about 25 F. at night), give your roses a weekly "potassium feast" in each of those six weeks. Potassium blocks the growth-promoting effects of nitrogen and phosphorous, thereby hardening the canes in time for winter.  I've been doing this for more than 20 years and I honestly can't remember the last time I lost a rose to winter weather here in Minnesota. Of course, I do other things to protect my roses from the Minnesota winter, as well.  Here is my 2013 article on winter protecting your roses:
 http://theminnesotarosegardener.blogspot.com/2013/09/winter-protecting-your-roses.html .

I learned this little trick in one of my first rose books: Burpee’s American Gardening Series, "Roses", by Suzanne Frutig Bales.  Here's a quote from Suzanne's chapter on winter protection:

“Potassium is an important mineral for sturdy stems and foliage.  Weekly feeds of a gallon of liquid potassium (1 tablespoon of muriate of potash (0-0-62), dissolved in 3 gallons of water) per bush, or a granulated feeding of potash magnesium (0-0-22), during the six weeks before the bushes go dormant, will give the bushes an additional boost for winter, extending their hardiness into another hardiness zone, perhaps two.  Excess potassium, when available in greater amounts than nitrogen and phosphorus, is known as the ‘potassium feast’.  It will block the growth-promoting effects of nitrogen and phosphorus, hardening the canes in time for winter.” 

I did a little independent research on this, a couple of years ago, by talking to Dr. Peter Bierman, retired University of Minnesota Professor of Soil, Water and Climate.  Peter told me that "... winter hardiness is one of the most important functions of potassium" and that the amounts recommended above..."would be a reasonable amount to apply for winter hardiness insurance and wouldn't be an excessive amount in terms of adding high salts."  That squares with my 20 years-plus experience in administering the potassium feast to my roses each fall.  

To clarify:  The proportions are: 1 TBP muriate of potash per 3 gallons of water (or 1 TSP per gallon).  So mixing in a 30 gallon trash container, you would use 10 TBP.  Apply one gallon of this mixture on each rose every week.  That’s not very much, but remember you’re repeating it six times. I also don't think the exact amount is critical and I usually err a bit on the side of a little more rather than less. (Please see my notes on using Potassium Sulfate below)

Several folks have asked me if they could "cheat" and do only three or four applications, using proportionally higher doses of potassium.  My answer is always: "I don't know, but it's probably better than not doing it at all."  However, my observations are that the roses harden off slowly, as the potassium applications continue over the six weeks and the weather gets colder.  By the end of six weeks, the canes have turned a lovely shade of red and look ready for the winter ahead.  With the canes thus hardened-off, they are less susceptible to the freeze-drying winter winds and naturally suffer less die back than if they their tissues were still soft.  I don't know if the roses will harden off as well with fewer, larger applications of potassium, but I suspect not.  However, don't let that discourage you if you get started late.  A couple of applications will be better than nothing.  Just try to get started earlier next year!

Another question is: where one can get potassium immediately to get started?  The answer to that is farm stores that sell fertilizers to farmers, who use potassium (potash) as an agricultural fertilizer.  Another source is suppliers to commercial growers and greenhouses.  In the Twin Cities, the primary sources for me have been Waconia UFC Farm Supply and BFG Supply in St. Paul (formerly J.R. Johnson Supply). It's sold in 50 pound bags for about $.40/lb.

It was pointed out to me by a reader in England that a very good alternative to muriate of potash would be potassium sulfate (0-0-50), which is 50% potassium and 18% sulfur.  This is interesting because adding sulfur to your roses in the fall has the effect of lowering the pH of your soil, which is desirable for most of us. A slightly acid pH around 6.0 (plus or minus) is best for roses.  (See my posting "Mind your pH":
http://theminnesotarosegardener.blogspot.com/2013/06/mind-your-ph.html.)
Since potassium sulfate has a bit less potassium, i.e. 50%, compared with muriate of postash at 60%, you would use a little more potassium sulfate, perhaps 1.25 or 1.5 tsp per gallon.  Again, I don't think the amount is super critical, so I would use 1.5 tsp/gallon to simplify things.

In any event, whatever form of potassium you use, I think this first step in the winterizing process is very important and I'm always amazed that many rosarians aren't aware of it.  Mid to late September is the right time for most of us to get started, so find some potassium and begin your roses' feast very soon (I made my first application last week).  I think you will be as pleasantly surprised by the results, as I have been over the years.

Here are two other articles on the potassium feast that I have previously published:

http://theminnesotarosegardener.blogspot.com/2012/08/potassium-special-k-ration-feast-for.html

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


Jack Falker
@mnrosegardener
jfalkersr@gmail.com

How Winter Affects Roses (Revisited)

This is the time of year when everyone in the cold zones should start thinking about winter-protecting their roses.  The sooner you get going, the easier the task will be in a couple of months.  I think this blog post, written in the winter of 2013/14, is worth revisiting for those of my readers who may have missed it. I would particularly call your attention to my articles referenced herein about the annual postassium feast, which should begin in mid-September, in time to "harden off" your roses for winter.

 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://theminnesotarosegardener.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://theminnesotarosegardener.blogspot.com/2014/09/potassium-feast-for-your-roses.html

http://theminnesotarosegardener.blogspot.com/2012/08/potassium-special-k-ration-feast-for.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
jfalkersr@gmail.com
September 17, 2015

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!