Winter wonderland

Although snow and ice can trans­form Ohio into a win­ter won­der­land, this same snow and ice can threaten the very trees and plants they adorn.

Win­ter injury may be rec­og­nized as exces­sive brown­ing of ever­green foliage, death of roots, bark split­ting or injury or death of flower buds. Win­ter sun, wind and cold tem­per­a­tures can bleach and des­ic­cate ever­green foliage, dam­age bark and injure or kill branches. Salt, used to remove ice from streets, side­walks and dri­ve­ways, is harm­ful to land­scape plant­i­ngs. The short­age of nat­ural food sup­ply that occurs in the win­ter months can force rodents, deer and other ani­mals to feast on bark, foliage, buds and roots. Snow and ice often breaks branches, and on occa­sion can top­ple an entire tree.

All is not lost. There are ways to pro­tect our pre­cious land­scape plantings.

First of all, it is impor­tant to choose hardy plants for the Ohio land­scape that can with­stand cold tem­per­a­tures. In cen­tral Ohio, we are in the USDA’s Revised Har­di­ness Zone 6a. Gen­er­ally, these plants can with­stand tem­per­a­tures of 10 to 15 degrees below zero. The USDA Revised Har­di­ness Zones Ohio map can be viewed at ohioline.osu.edu/hyg-fact/1000/pdf/1648.pdf. Be sure to check the plant label or ask the nurs­ery about suit­abil­ity to zone 5b.

Healthy plants accli­mate to colder tem­per­a­tures. For many species, the short­ened hours of day­light in late sum­mer ini­ti­ates the hard­en­ing process by slow­ing veg­e­ta­tive growth. The amount of nitro­gen fer­til­iz­ers applied should be reduced after mid-July and stopped by late sum­mer. Ide­ally, plants should enter the win­ter sea­son as healthy as pos­si­ble but not rapidly grow­ing. Cool tem­per­a­tures also con­tribute to cold har­di­ness, par­tic­u­larly freez­ing tem­per­a­tures. Gar­den­ers can assist the cold har­di­ness process by water­ing plants late in the grow­ing sea­son thus decreas­ing the like­li­hood of tis­sue des­ic­ca­tion, which is one of the most com­mon forms of win­ter injury, par­tic­u­larly in evergreens.

Another win­ter haz­ard is sun scald, which is char­ac­ter­ized by elon­gated, sunken, dried, or cracked areas of dead bark typ­i­cally found on the south or south­west side of a tree. On colder days, the sun heats up the bark to the point where cam­bial activ­ity is stim­u­lated. Later, the sun is blocked by a cloud, hill or build­ing and bark tem­per­a­ture drops rapidly, killing active tis­sue. Young trees are par­tic­u­larly sus­cep­ti­ble. Sun scald can be pre­vented by wrap­ping the trunk with a com­mer­cial tree wrap or plas­tic tree guard.

There are sev­eral other ways to pro­tect plants in the land­scape includ­ing mulching, tying, anti-desiccants, and wrap­ping. Mulch main­tains more even soil tem­per­a­tures and helps retain soil mois­ture. Gar­den­ers should apply a 2 to 2.5 inch layer of mulch after the soil freezes to keep the soil cold. This prac­tice reduces injury from plant roots heav­ing caused by alter­nate freez­ing and thaw­ing. Bark prod­ucts, com­posts, peat moss, pine nee­dles, straw, hay and even dis­carded Christ­mas trees make ideal mulching materials.

Mul­ti­ple branched plants such as junipers and yews may be dam­aged by the weight of snow and/or ice. Fas­ten­ing heavy twine at the base of the plants and wind­ing it around and upward to the top and back again can help pro­tect against breakage.

Win­ter cold and winds cause exces­sive tran­spi­ra­tion (foliage water loss) at a time when roots are in frozen soil and unable to replace lost water. This causes des­ic­ca­tion and brown­ing of the plant tis­sue. Apply­ing an anti-desiccant in Decem­ber and Feb­ru­ary reduces the threat of injury. Wraps of burlap or can­vas can also pro­tect against des­ic­ca­tion from sun, wind and salt. It is impor­tant to leave the top uncov­ered as some light is nec­es­sary dur­ing win­ter months.

Rab­bits, mice, moles and deer are forced to seek alter­nate food sources dur­ing extended peri­ods of snow cov­er­age. They often turn to flow­er­ing crabap­ple, moun­tain ash, hawthorn, euony­mus and vibur­num, among oth­ers. Girdling of stems by rodents will kill the plant if com­plete, and if par­tial, will cre­ate wounds for bor­ers and other dis­ease organ­isms to enter.

Gar­den­ers should pro­tect stems and trunks of these plants in late autumn with plas­tic col­lars cut in a spi­ral fash­ion so they many be slipped around tree trunks. Rodent repel­lents sprayed or painted on trunks, stumps and lower limbs may also be effective.

Gar­den­ers invest sig­nif­i­cant resources in their home land­scapes and will reap the ben­e­fits of a lit­tle win­ter care. More infor­ma­tion on this timely topic is avail­able at ohioline.osu.edu/hyg-fact/1000/pdf/1648.pdf.

Michele Pear­son is an OSU Exten­sion Mas­ter Gar­dener volunteer.

Posted by Master Gardener on Feb 18 2012. You can follow any responses to this entry through the RSS Feed. Comments can be made below.