Feature Story
Winter Wellness for Landscape Ornamentals
A
brutal snowy winter- a mild cold winter – is one better for tinue to push new growth. Cut back on watering practices plants then the other? Not necessarily. Damage to plants in the late summer and early fall. This holding back of water due to cold temperatures can occur during several times of and nutrients supports early development of hardiness for the year: spring and fall; the coldest part of winter; and when the winter ahead. cold temperatures occur after a warm period of weather. An However, before the ground freezes in the late fall/early early snow that stays around or gets replenished through the winter, give trees and shrubs a good watering, enough to winter months serves a good insulator against cold damage. reach an 8-10 inch depth once a week. When the ground Cold temperatures cause injury to trees, is frozen, it may not absorb rain washrubs and ornamentals in the landter or snow readily. The moisture in the scape. The xylem, conducting vessels soil can be absorbed by the roots below of plants, in small branches of trees and the ground. During a dry winter, hollies shrubs can be damaged by cold temperand evergreens or plants located under a atures, but the injury is not noticed until roof eaves may need to be watered once a the spring when the growth is slowed, month if there is a warm spell. Be careful there are less flower buds or the branch around walk ways and parking lots, as you is completely dead. This type of injury do not want to create an icy situation. usually occurs in mid-winter. These cold Sunny winter days can cause injury winter temperatures may also kill dorto trees. Bark temperatures can be 10oF mant flower buds and cause dieback in warmer then air temperatures as the overwintering evergreen plants. A cold sun shines on the tree. A rapid drop in winter with little or no snow may be temperature may cause and injury called considered mild, but drying winds will sun scald. Frost cracks can occur when take moisture out of plants. there is repeated injury from temperature Spring frosts can damage the tender fluctuations due to sun exposure. Newly shoots, flowers and fruits of plants that planted trees and thin barked trees such may have started coming out of doras Cherry, Crabapple and Maple are susWrap young trees with reflective white tree guards mancy too soon due to warmer than Credit: University of Minnesota ceptible to these injuries. Over time, frost average winter temperatures. Tempercracks go deeper into the trunk of the tree atures several degrees above average minimum temperatures and a callus forms along the injury. The wood inside might in the late fall before plants have reached their maximum decay, leading to structural problems. Evergreen trees are less dormancy or hardiness can cause injury to plants, including susceptible to frost cracks then deciduous trees. Lone trees deciduous trees and shrubs that have already lost their leaves. in the landscape are an easy target for frost cracks. Planting Plants naturally prepare themselves for the winter by go- lower growing trees or shrubs around the tree can provide ing into dormancy. Plants do need those cooler tempera- some protection. tures and shorter days of the fall and a reduction in watering Fortunately trees can be protected from sunscald and frost and nutrients to prepare themselves for the winter. To aid cracks. Using a polyurethane spiral wrap or wrapping Kraft the plants in their preparation for winter, avoid fertilizing paper around the trunk can help keep the trunk temperatures ornamental plants after mid-July/early August. Fertilizing constant. The wraps can also provide protection from wildstimulates new growth, which will not be hardy enough for life damage during the winter months. The wraps should be winter. The plant may not go into dormancy – it will con- applied in the fall, but removed in the late spring. Apply the
40 FALL | 2020
