University of Minnesota Extension, Stearns County News
June 4, 2014
Source: Beth Berlin, Extension Educator-Horticulture
University of Minnesota Extension
Stearns & Benton Counties
Plants Still Feel the Effects of Winter
By Beth Berlin, University of Minnesota Extension
ST. CLOUD, Minn. (06/04/14) — Did some of your trees and shrubs not leaf out or seem to skip having flower blooms this spring? This winter really was a battle for our plants. Many plant species struggled because of the dry environmental conditions it has endured for the last few years plus the harsh winter. The question now is does the plant have a chance and what can we do about it?
Regardless of the adequate snow cover which serves as an insulation layer; this winter was one for the record books. Soil frost depths, soil temperatures, wind chill, and repeated daytime and overnight lows of below zero caused very challenging conditions for our plants and us. In addition the winter persisted on and it was a cool wet spring, which did not give relief to the stressed plants.
In the landscape spirea shrubs have seemed to be a go-to, hardy shrub for years. However this spring many spireas haven’t leafed out and look dead. The harsh cold winter apparently affected the spirea plants pretty hard. Spireas are rated for USDA (United States Department of Agriculture) hardiness zone 4. The USDA Plant Hardiness Zone Map, which was revised in 2012, is based on the average annual minimum winter temperature, not extreme low temperatures that were reached or could be reached in the future. Therefore, the cold and very long winter, plus other environmental conditions appear to have set back the spirea even though predominately the southern half of Minnesota is rated for zone 4. Damage has included dead stems from only a few to the entire shrub. The best thing a homeowner or municipal maintenance worker can do is cut them back to the ground level or where there are signs of leafing out, and allow the plant some time to recover. In some cases pruning back only the dead stems may leave it looking unattractive and it may be best to just cut it all back to allow for a more even appearance. After doing this and still no signs of new growth, unfortunately it is time to replace the plant.
Other plants such as Eastern redbud, certain varieties of apple trees, forsythia, cherry bushes, and many more did not bloom. All these species and others are marginally hardy for this zone, and because of the harsh winter they too suffered. Flower buds are actually not as hardy as leaf buds so this is why your tree or shrub may not have flowered out but now is leafing out. The best thing to do is just make sure other environmental conditions throughout this growing season do not put more stress on the plant. Ensure it is receiving adequate water, watch for pests, and avoid mechanical damage with lawnmowers or other equipment. For future planning and purchasing, look for more hardy varieties.
The question is then; will these plants survive and bloom next spring? Ultimately it will depend on this year’s growing conditions and next winter. Many of the marginally hardy shrubs or trees years ago had inconsistent blooms when in general the winters were harsher.