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 When selecting roses, always select cultivars that are able to
tolerate the coldest temperatures in your area based on USDA
hardiness zone maps. One of the ways to protect roses for the
winter is to be sure they go completely dormant. To accomplish
this, stop fertilizing early enough so growth slows down. No
fertilizer should be applied after August 15. To further
encourage dormancy, stop dead-heading or cutting flowers after
October 1 and allow the plant to form hips.
There are many methods to provide winter protection for roses.
The whole idea of winter protection is to keep the plant
uniformly cold and frozen all winter and prevent the damaging
effects of alternate freezing and thawing. Whatever the method,
don't begin covering plants too early. Wait until a hard killing
frost has caused most of the leaves to fall, and the temperature
has dropped into the teens for several nights. Prior to
covering, remove any foliage or other debris that might harbor
disease for the next season.
Before covering, some tall roses may need minor pruning to
reduce their height, and tie canes together to prevent wind
whipping. Pruning at this point should be kept to a minimum.
Most pruning will be done in the spring to remove dead and
diseased canes.
The most common way to provide winter protection is to pile or
"hill-up" a loose, soil and compost mix around and over the
plant about 10-12 inches deep. A variety of hilling materials
can be used, but the key is to be sure that the material is well
drained. Wet and cold is far more damaging than dry and cold.
Soil that is used to "hill-up" plants should be brought in from
outside the rose garden. After the soil mound has frozen, the
mound can be covered with evergreen boughs, hardwood leaves, or
straw to help insulate and keep the soil frozen.
A variation of the "hilling" method is one utilizing collars. An
18-inch-high circle of hardware cloth or chicken wire is placed
around the plant. The collar is filled with soil, allowed to
freeze, then mulched with straw. The benefit of the collar is
that it holds the soil in place all winter and prevents it from
being washed or eroded away.
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Another popular method of winter protection for roses is the
use of styrofoam rose cones. If these are used, they need to be
used properly. First, don't cover the plants too early. Follow
the general timing guidelines. Second, cones need to be well
ventilated by cutting holes around the top and bottom of the
cones. This helps prevent heat build-up on the inside during
sunny winter days. It is also advisable to mound soil around the
crown of the plant before putting the cone in place. For
extremely tender varieties, some rose growers cut the top off
the cone and stuff it full of straw for added protection. It is
also a good idea to weight the cone down with a brick or stone
to keep it from blowing away.
Climbing roses offer more challenges. For marginal varieties,
climbers may need to be removed from their supports and bent to
the ground, then covered with six inches of soil and mulched.
When laying climbers on the ground for covering, one needs to be
very careful not to injure or crack the stems. As the weather
gets colder their long stems are more rigid, and they are easily
broken.
Another method that can be used is to physically pack straw
around the canes while they are still attached to the trellis or
support. The straw is held in place with twine to keep it in
place over the winter.
Generally knockout roses don’t require special care in hardiness
zone 5 or south. We are in zone 5a or b. If you do want to do
something because of prior problems, you can mulch the crown
area. Some go to the extreme and burlap them or put wire around
them and fill with leaves, but that is entirely up to you. The
basic care is a pruning, if needed, in the early spring to size
or shape.
[By JOHN FULTON, COUNTY EXTENSION
DIRECTOR SERVING LOGAN, MENARD, AND SANGAMON COUNTIES]
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