Winter injury
Not an infection: winter sun, wind, sudden temperature swings and deep cold dry out or kill leaves, buds, bark and roots
| Type | Not an infection |
|---|---|
| Cause | Not an infection: winter sun, wind, sudden temperature swings and deep cold dry out or kill leaves, buds, bark and roots |
| When | Damage happens in winter; it shows in late winter and spring. |
About
Damage from winter that often shows up in late winter or spring: browned evergreens, dead branch tips, killed flower buds and cracked trunks. Swings between mild and very cold weather do more harm than steady cold.
Also called winter injury, winter burn, winter damage, winter desiccation, winterkill, frost crack, frost cracks, evergreen browning, winter dieback
How to recognize it
Symptoms
On evergreens, needle and leaf tips turn brown in late winter and early spring, with browning spreading down from the tips, often worst on the sunny or windy side. Deciduous shrubs show dead twig tips and flower buds that fail to open. On trunks, frost cracks are long vertical splits, often on the south or southwest side, that can reopen every winter; sunscald leaves sunken, cracked dead bark in the same spot.
Often confused with
Road and sidewalk salt also browns evergreens and kills branch tips near drives and roads (see Road salt injury). Bark sunscald on fruit trees has its own page (see Sunscald).
Worse when
Dry fall soil, sunny winter days with frozen ground, a sudden cold snap after a warm spell, little snow cover, late-summer pruning or feeding that pushes soft growth, and thin-barked young trees.
How it spreads
It does not spread from plant to plant.
When
Damage happens in winter; it shows in late winter and spring.
What to do, gentlest first
This is not an infection, so sprays for diseases won't help. Fix the cause below.
Water well in fall Prevent
Keep watering trees and shrubs, especially evergreens, through dry falls until the ground freezes, and mulch 3 to 4 inches deep (pulled back from trunks) to insulate roots.
Plant and prune with winter in mind Prevent
Choose hardy plants, and put marginal ones like broadleaf evergreens in spots sheltered from wind and winter sun (north or east sides of buildings). Don't prune or fertilize in late summer.
UMN says not to prune evergreens after August.
Wait, then prune By hand
Wait until mid-spring before cutting brown evergreen growth, since the buds often leaf out again. Then prune dead branches back to live tissue.
Don't paint or tar bark wounds or frost cracks; let the tree close them on its own.
Burlap screens and trunk guards Barrier
Set burlap screens on the south, southwest and windward sides of exposed evergreens, leaving the top open; don't wrap the plant itself. Put white trunk wrap or guards on young thin-barked trees in fall and take them off in spring.
Anti-desiccant sprays get mixed reviews: Morton Arboretum says they may help if applied by the label in late fall, while UMN Extension found them not effective.
Plants it affects
Apple (backyard tree), Arborvitae, Boxwood, Cherry (sweet and tart), Eastern white pine, Flowering crabapple, Forsythia, Holly, Juniper, Red maple, Rhododendron, River birch, Southern magnolia, Sugar maple, Yew
Sources
Planting dates and advice are general guidance; check with your local Cooperative Extension office for your area.