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Many landscape plants used in Wyoming need some protection over the winter. It is a must for roses, as even the ones considered
to be hardy tend to suffer cane damage. Here is why and how to protect your roses.
When you plant roses which are advertised to survive zone 4 or colder, yet in spring they've had massive cane damage,
you wonder, "Why?"; For a rose to survive Wyoming winter, buying a hardy variety is important but the process of
acclimation and de-acclimation is vital.
In order for plants to get through winter successfully they must go through a period of acclimation (fall) and de-acclimation
(spring). This process induces the plant to undergo chemical and physiological changes to aid it in coping with cold weather.
Roses with this ability have acquired it by adaptation to cold environments over millennia. This is why some roses are hardier
than others.
Acclimation occurs in fall as the plant reacts to the shorter day length along with colder temperatures in the air and
soil. Shorter days mean plants spend less time manufacturing and using food, so much of the food processed is stored in the
stems and roots. It also reduces the amount of food being prepared, and as the soil cools down, the roots work more slowly
to absorb water and nutrients. Abscission, which is the technical term for leaf drop begins; the first indication is the color
change of leaves. Dropping leaves allows the plant to keep food stored for use later on in the winter.
Water less as the days grow shorter. As each day continues to shorten and temperatures get colder, plants reduce water
in their cells, which enables them to withstand freezing temperatures without being damaged. Lower the amount of water you
give your roses gradually; this triggers dormancy processes and toughens the plants for winter stress. Right now roses should
be watered no more than every ten days. Come November, water should be given no more than every two weeks. Throughout the
winter season, water should be put on roses when the temperature is above 40 degrees, and the two week schedule is a good
guideline unless it is much warmer for long periods of time or much colder. Many gardening guides for Wyoming tell you to
water plants once a month in the winter. Roses will do better with at least two waterings per month.
A healthy rose is most important for surviving Wyoming winters! Don't neglect your roses in the summer and expect them
to come through winter without damage. Hardy roses are no exception to this rule. If plants go into winter weakened from lack
of water or nutrition, ravaged by insects or disease that has gone unchecked, you can count on casualties. Clean up all fallen
leaves and debris from the rose bed, as these too will harbor pathogens. If there is insect or disease damage, spray with
lime sulfur/dormant oil before temperatures go below 20o, which will help suffocate over-wintering eggs and spores. This can
be done in very early spring instead, if that is a better time for your schedule.
Newly planted roses should not be allowed to flower during the first year in the ground. Flowers absorb large amounts
of energy from the plant and it is less likely the plant will survive winter cold if it has flowered throughout its first
season. That said, if there are any buds coming on now you may allow a few of them to open on the plant. The trick is to leave
the flowers on the bush without deadheading, so the fruit (hip) will form. This is another process roses use to become dormant.
On established roses from which you have removed blossoms all season to encourage new buds, you now leave the flowers on and
let them go to seed. This rule does not apply to roses which bloom only once a season or to wild roses. Those are genetically
geared to go dormant when fall comes, but it still helps to reduce watering and feed 0-10-10 fertilizer.
This is a good time to apply 0-10-10 fertilizer. September is best but up until early November will work, depending on
the weather. Potassium and phosphorus builds up plants to handle times of stress. Once it becomes really cold, roses can only
use the nutrients they have stored. Leave manure for the spring. You don't want all that nitrogen leaching away with the melting
snow or more importantly, inducing new growth which could be injured or killed by frost.
What happens if you have mild autumn weather into early winter where the temperatures don't continually get colder but
stay relatively warm, then all at once dive to well below freezing OR winter arrives early before the plants have had sufficient
time to acclimate?? The answer is you get damage, known as winterkill. Too much water in a cell and when it freezes it expands
and the cell wall bursts. The part of the plant that has not sufficiently removed water from its cells will die. If you have
reduced the amount of water given, it will minimize the damage.
Late October to mid November is generally a good time to put your roses to bed. The aim is not too soon nor too late but
just at the right time. This is complicated by the fact that fall seasons can be unpredictable in Wyoming. While in recent
years, autumn has been decidedly warmer than usual, it is not something you can count on. The thing to do is monitor the weather
reports and have your mulch and cover materials ready to go should a cold snap be predicted. You know its coming; your readiness
to protect roses before a freeze occurs will increase their chances of survival.
If you buy mulch by the truckload, place it where you can quickly spread where it's needed. You can pile it around the
roses and heap it over the plants when the weather gets below freezing. Save newspapers and roll or fold them to lie on the
ground around the base of the roses. If you're planning to use straw, it may be more effective to leave it in flakes rather
than strewn over the plants. Some people set whole bales out rather than break them up. Straw, leaves and all lightweight
materials need to be contained or the wind will remove them from your garden.
You will need to contain the materials you're using to protect your roses. It won't help to cover the beds with straw,
for example, and have the wind blow everything away. Protection from wind is one of the most important things you can do for
roses during Wyoming winters. Wind damage not only takes the form of breakage but of desiccation. Low humidity and constant
wind movement can drain rose canes of moisture beyond its ability to recover. Planting windbreaks, building fences or heaping
mulch into a barrier on the west and/or north side of your plants will be helpful. Erecting temporary barriers of commercial
wind fence if nothing else is available will go a long way towards safeguarding your roses over the winter. Snow is an insulator
for plants; if you can arrange your fencing to drop snow over the rose beds when it comes, you will have both protected and
watered them at the same time.
Some types of roses, i.e., hybrid teas, grandifloras and floribundas are usually not very hardy, partially due to their
china rose ancestry and because they are grafted. In order for them to have a chance of surviving, the bud union or graft
needs to be at least four inches below ground level. A graft is very tender and the rose can die off if it is damaged by freezing
during winter, leaving the rootstock to come up the next year and you have a whole different plant than before.
Canes should be tied together and mounded up as high as you can with insulation in the form of bark, straw, soil, newspaper,
etc. The mulch insulates the roses from temperature fluctuations which are so damaging. If you're unsure how hardy your rose
is or if you've just planted it, then by all means mound it up as high as you can with soil, not mulch. Soil insulates much
better!
Some gardeners use tomato or peony cages around their roses and build winter protection around these frames. Chicken wire
cages are useful if they're staked to the ground. The frames can both be filled and heaped up around the outside with mulch.
Landscape fabric, old sheets or netting can also be wrapped around the plants once the mulch is in place. Do not use plastic
unless it is fully perforated with holes for air circulation.
Prune off any damaged or diseased canes back to healthy wood. You can dab a bit of wood heal on the wound to prevent cane
borers from entering. With this exception, pruning is best done in the spring for cold climates.
With high winds or lots of snow in your area, it's good practice to tie the canes together so that they will not break
off. If you have a climber and have managed to develop nice long canes, it is a good idea to untie the canes from its support
and lay them on the ground, tying together in bundles and covering them with mulch. You'll need heavy gloves for this procedure!
Old pantyhose, baling twine, cheesecloth and fabric strips are a few items to consider for tying. If the canes cannot be laid
on the ground, it is a good idea to wrap them in burlap or weedmat to protect them from the wind.
Winter watering is very important when temperatures are above 40 degrees. Roots will still be active and will benefit
from periodic watering in the winter. If you have made a well around the base of each rose to hold water, this must be filled
in as it will hold water which can become ice and damage the base of the rose. Bark splitting and/or death of the plant can
occur if water freezes and thaws here over the winter. While you're at it, mound up soil over the plant base so that water
will flow away from it.
Roses in containers need to be brought in where they are kept cold but not below freezing. They should be checked periodically
and watered regularly, but not fed. Some light should be available, as the plants will decline quickly if kept too dark.
Once you've protected your roses as best you can, keep an eye on them as the winter progresses. If you see mold or fungus
forming on the canes, stir up the mulch to allow air circulation. If the wind has uncovered portions of the plant, heap it
back up or replace with new mulch. If the weather is very windy and dry, water a little extra to keep the roots moist.
One can never predict what winter will bring to Wyoming. This fall 2007 has seen fairly regular rainfall and gradual cooling
overall. If you have fed and watered your roses consistently over the summer season, they will be well on their way to be
prepared for the winter. Cover your roses, water regularly and check occasionally over the winter; these tips will help bring
them through the variable weather to come.
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