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Winter Protection

Posted by diamondust PA. (My Page) on
Wed, Nov 12, 08 at 23:09

Can someone please explain the theory of how and why of winter protection i.e. does one need to protect to or less than 32 degree temps or protect only from the wind. How do we protect from temps of 5 or 10 deg. -- will stems freeze -- won't the Heart of the Rose freeze at these temps even if covered? If I just protect from the cold wind is that enough? There must be some scientific evidence out there somewhere that can explain all this -- maybe some experments that have been conducted?
Would just straw covering the heart be enough?
I just want to know how best to protect my Roses and maybe try some new methods.

Thanks,
Tom


Follow-Up Postings:

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RE: Winter Protection

I probably won't answer all your questions but this is what I learned many years ago from a roses expert when I first started growing roses (late 70's) & it has worked well for me. He said "you want your roses exposed to 28F or colder at least 3 different days before you put on any winter protection/mulch". This rule has worked well for me but I always had one question, "is there some limit to the 'or colder part'?" A few years ago another rose friend told me about a study done a Boerner Botanical Gardens in Milwaukee that came up with a 20F rule, "roses can take down to 20F but if the temp is going to drop below 20F, you need to cover them". I just cover my roses last weekend because they had been exposed to way over 3 days with temps of 28F but no 20F days yet however the weather reports were for 17F on Tues so this is why I decided to cover them. One statement that you often hear is" you cover your roses & other tender plants to keep them WARM". This is WRONG, you cover your plants to keep them COLD & to prevent the ground around them from going thru 'freeze-thaw cycles' which damages & kills the roots. For covering my roses: my 'in the ground rose' I use collars & fill them with wood chips that I get 'free for the hauling' from my city's forestry dept. & for my potted roses, I remove them fom their pots, lay them on their sides in a trench in my vegetable garden & cover them with soil. Hope this answers some of your questions.


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RE: Winter Protection

The closest thing to a 'scientific' investigation of winter protection was a survey done many years ago by some rose societies in Illinois. The results of the survey - various forms of winter protection vs. rose survival - were that there was no scientific basis for anything. My personal experience is that the biggest reason for winter protection in zone 5 has to do with the emotional state of the gardener and nothing to do with the rose.

From observation, cane death for most HTs and Fls occurs somewhere around zero. Various books have different ways of expressing this, but it all boils down to about the same thing. However, covering the rose in an area with winter ups and downs just leads to cane death from canker.


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RE: Winter Protection

This is why it's important to buy roses hardy to your growing zone. Many roses cannot take freezing temperatures.
As stated above, the idea is not to protect from freezing, it's to keep the soil from the freeze/thaw cycle which can break apart roots and kill plants that prematurely break dormancy.
You begin your winter protection by planting the tender bud union/graft 4-6 inches below the soil surface. This may slow down first year growth but overall it's better for the bush in cold winter climates. It also promotes rooting on that portion of the canes above the graft and below the soil surface, eventually causing the plant to go own root meaning you don't have to worry about the graft dying, or suckering from the root stock.
That's where buying cold hardy varieties come in. Many can take temperatures to minus 40 degrees with minimal or no cane damage. Other will die back, often to ground level but regrow each year from the roots.
Right now I have some 450 roses which require no more than Nature's fallen leaves to survive my cold winters in zone 5a. Most are hardy Canadian or Griffith Buck varieties plus others that have proved to be hardy in my area. My 30 or so hybrid teas have proved to be hardy even though I have to prune them back to a couple of inches each spring.
Same with my 40 or so climbers. A few will have green to the tips but most require severe pruning each spring.
This is something I accept in order to grow roses in my area which can get down to minus 20 for brief periods each winter
There are a number of good books that can give you excellent advice regarding cold climate roses. Among them are "Growing Roses in Cold Climates" by Jerry Olson and John Whitman, "Hardy Roses" by Robert Osborne, "Roses for the North" from The Minnesota Agricultural Experiment Station, and "A Year of Roses" by Stephen Scanniello. Joining a local Rose Society gets you great advice from those in your area who can tell you which roses do well for them with minimal winter protection.
While questions here will get you advice from many, take with a grain of salt that advice from anyone living in a zone warmer than yours unless they have experienced growing them in colder zones.
When buying roses, add a couple of zones to that stated in the bush's description. Most of these nurseries are interested in selling roses so they'll stretch the hardiness zone a little. Buy from those places located in colder areas as they tend to grow only those varieties that will survive our winters. Avoid resellers, those who buy roses grown in warmer areas to resell in cold areas.
Many of the mailorder nurseries are resellers. Almost all local garden centers and big box stores get their stock from warmer areas or grown in greenhouses. Otherwise they wouldn't have plants in bud and bloom in May when most gardeners are sprucing up their yards. In many cases these will die the first winter unless you go to great extremes to winter protect.
I know. Many of the roses pictured on my website had to be winter protected to survive. Only a disability forced me to grow only the hardier ones.
The southern portion of your state can grow many of the less hardy varieties without protection but a cold winter would quickly let you know which ones not to try without winter protection.

Here is a link that might be useful: Rosenut's webpage


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RE: Winter Protection

I went through the weather records last night and found little correlation between winter kill and lowest temperature of the year.

Year Lowest Temp Roses that died number of plants
2002 15f Henry Fonda out of 13 plants
2003 1f 12 roses of all types out of 27 plants
2004 -4f two mini tree roses out of 26 plants
2005 -7f all survived
2006 -6f Pristine died out of 47 roses including 17 HTs
2007 1f VH died out of 82 roses
2008 6f all survived out of 118 roses including 35 HTs

Ironically, the two tree roses that died were buried according to the Minnesota tip method. In our garden, there seems to be a better correlation between winter protection, which we started for the 2004 year, than temperature. Winter protection seems important in our climate, which has unreliable snow cover and plenty of freeze thaw. Many new rosarians to our local club report significant winter kill.


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