Winter isn’t giving up easily this year, but we know spring will come — eventually — and with it may come signs of damaged trees and shrubs. Temperature drops to minus 20 degrees is cold enough to leave behind some Some fruit tree species that may have adverse effects from this winter’s extreme cold are peach and sweet cherry trees. Iowa gardeners should expect poor crops on peaches and sweet cherries this summer. Peach trees are not reliably cold hardy in much of Iowa and temps below minus 18 will destroy flower buds on peach trees, while temps of minus 25 or below may destroy the peach trees themselves.
Sweet cherry flower buds are slightly more cold-hardy and can survive temperatures of minus 20, but again, lower temps can damage the tree itself. Signs of damage include dieback of twigs and branches or entire loss of a tree. However, the cold winter temperatures should not have damaged apples, pears and sour (tart) cherries.
Most native Iowa trees and shrubs are well adapted to our climate and should have suffered little or no damage. Marginally hardy plants, like Japanese maple (Acer palmatum), flowering dogwood (Cornus florida) and Japanese flowering cherry (Prunus serrulata) may have been damaged since the cold hardiness of these varieties is minus 20. Damage could include the entire tree not coming back or branch dieback.
According to Richard Jauron, extension horticulturalist at Iowa State University, flowering quince (Chaenomeles spp.) and some forsythia cultivars, including Lynwood Gold and Spring Glory (two popular forsythia cultivars), most likely will have damaged flower buds resulting in few, if any, flowers in spring. But the leaf buds on these shrubs are more cold hardy than the flower buds and they should leaf out normally in spring. Other forsythia cultivars, such as Meadowlark and Northern Sun, should be fine since these varieties are more cold hardy and can tolerate temperatures to minus 30.
Besides the frigid temperatures this winter, we have had long sustained snow cover, which results in deer and rabbits feeding on and damaging trees and shrubs. Among evergreens, arborvitae and yews are most susceptible to deer dining in winter. Depending on how much of an evergreen a deer has eaten will determine the extent of damage. If there is an absence of buds (growing points) on the lower branches, they won’t come back and will stay bare. If buds are present, the lower branches will produce new growth in spring, appearing by early summer.
Rabbits will chew off small branches from shrubs and feed on the tissue between the bark and wood of trees, giving the appearance that the bark has been stripped away.
If rabbits remove the tissue down to the wood and go completely around the tree’s trunk, the damaged tree is effectively girdled. Girdling disrupts the downward flow of food from the tree’s foliage to the root system and eventually kills a tree.
Lisa Slattery is a Linn County Master Gardener.