The first landscape planta noticed were roses. We have a trial in Snyder Park Gardens & Arboretum looking at varieties resistant to rose rosette disease. While we haven’t seen this disease at this time, the roses took a bit of a beating with the cold weather.
Another landscape plant is boxwoods. If you recall, I talked a lot about boxwood in the past two years. Last year it was the box tree moth and the year before it was Volutella leaf and stem blight due to damage from temperatures the previous December.
Boxwoods in my area are exhibiting symptoms of winter burn. This is different than stem dieback. Because they are broadleaf evergreens and store their sugars in the leaves, and remain on the plant all winter, there is some desiccation injury.
Desiccation injury is different than stem dieback. The damage is to the foliage and is usually prevalent on the outer side that is exposed to either westerly winds or southern facing winter sun and wind.
The leaves lose moisture faster than they can replace it in the winter because of frozen soil. The result is brown leaves, but the stems are still green. If it’s winter burn, the term we use for this type of damage, the leaves will drop and new leaves will emerge.
If it’s stem damage from severe cold temperatures, the stems may die. And, if you had Volutella stem and leaf blight in the past, you may see it again this season. Time will tell.
At this point, the recommendation is to wait and see. I wouldn’t prune anything unless you are sure the branches and stems are dead.
In terms of the roses, you can start pruning them now as well. From my observations, the roses aren’t completely dead to the ground, but rather dieback to around one foot or so.
If you see brown stems on the rose, cut the brown out, back to the viable green tissue. At this time, you can also see new bud growth which will help determine how far back to cut.
One thing to keep in mind, you may find a healthy bud on a half dead stem. Eventually this stem will die completely. Since it’s a rose and you likely cut it back each season, let it go this year and watch to see what happens next.
And of course, we are at that time of the year when daffodils, tulips and other bulbs are out of the ground and some of the early varieties are in bloom. Remember that the flowers are the most sensitive to freezing temperatures or even frosts.
The foliage can withstand damage from low temperatures and still bloom if the buds aren’t exposed. They don’t die completely; they may just look straggly for this season.
After they finish blooming, let the foliage grow to store up sugars in the bulb for next season.
Pamela Corle-Bennett is the state master gardener volunteer coordinator and horticulture educator for Ohio State University Extension. Contact her by email at bennett.27@osu.edu.
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