Winter Injury Plant Material Maintenance

Temperature Fluctuation Damage can occur from:  Rapid/extreme fluctuations in temp  Extended mild weather can de-acclimate plants, leaving them vulnerable to rapid temp drops

Low Temperatures Use USDA Hardiness Zone Rating  Several mild winters can lull people to believe plant will be hardy. (Cutleaf Japanese Maple) Plant marginally hardy plants in protected sites.  East side of building  courtyards

Frost Cracks Long cracks on the south-southwest side of thin barked trees  Due to temp fluctuations between day and night; uneven contraction of the wood  Ex European Linden, Red Maple, Norway Maple

Frost Cracks on Green Ash

Sunscald Injury Very similar to frost cracks; damage is an elongated canker  Winter sun is lower in the southern sky  The lower angle of the sun can directly heat the south and southwest side of a tree trunk during a sunny winter day  Subsequent freezing, night-time temperatures damage cells  Thin barked trees w/ smooth, dark bark are particularly susceptible

Sunscald on the SW side of a Chokecherry tree

More Sunscald Injury

Winterburn on Evergreens Browning or scorched needles Due to desiccation  Winter sun & wind dries leaves  Transpirational water loss  Replacement water unavailable (frozen) Can apply an anti-desiccant to prevent injury  Reapply throughout winter

Snow & Ice Breakage Heavy snow and snow piled on plants from driveways and walks Multi-stemmed evergreens most prone to damage Gently remove heavy snow from branches Do not remove ice from ice-encased branches

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Salt Damage Damage appears in spring and early summer  Scorching of leaves Avoid heavy salt usage near plants Use salt tolerant plants near walks and drives if salt needed. Most salt damage occurs from late winter applications of salt. Avoid if possible. Use calcium chloride, or other safe de-icer, instead of rock salt

Girdling by animals Mice/rabbits/voles feed on bark and girdle branches. Growth beyond girdling dies in spring Wrap trunks with screen wire or hardware cloth

Minimizing Winter Injury Select hardy plants Avoid late summer pruning and fertilizing Water plants during dry periods until ground freezes Use mulch to conserve moisture and insulate roots Protect evergreens with screening Use anti-desiccant if needed Wrap trunks to protect and remove in spring Use safe ice-melting products

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