Frost Injury and Ice Damage

	River birch (Betula nigra) broken by ice buildup

Zone hardy plants can be injured during unusually cold temperatures, when temperatures drop rapidly or when temperatures fluctuate from warm to below the upper 20 degrees F. Typically, late spring and early autumn frosts do the most damage to active plant tissues that have not hardened off to withstand the cold.

With below freezing temperatures, water in plant cells freezes forming ice crystals that expand as they freeze and rupture cell walls. The effect is similar to pricking a hole in a water filled balloon. The special ‘glue’ holding the plant cells together leaks out and the plant cells collapse.

Flower buds, vegetative buds, stems, crowns, or even whole plants may be injured. The damage starts with the softest, actively growing tissues like new leaves and tender shoots. Later plants become limp, blackened, and/or distorted. Damage to stems can remain hidden until active spring growth starts. Evergreen shoot tips curl downward and may turn red or brown 1 – 2 weeks after the damage.

Integrated Pest Management Strategies

1. Proper plant selection and placement. Use plants that are zone hardy for your planting area. Avoid placing sensitive plants in low areas where colder air collects.

2. Provide protection. Protect container plants over winter by sinking into the ground, heavily mulching them or moving them to protected areas.

3. Good culture. Avoid nitrogen fertilizer in late summer (after July). Plants respond by producing soft, sappy growth that is vulnerable to cold damage. Mulch after the first hard fall frost to insulate soil surfaces. Feed damaged plants a balanced fertilizer.

4. Don't prune too early. Wait until after the last spring frost date, when the plant is actively growing, to prune dead areas. It is an advantage to be able to see for sure the extent of the damage. Prune the affected areas to a healthy new bud directed outward from the center of the plant. Proper cutting helps the plant by directing its growth without the need for later fix-up cuts. Fewer, good cuts are better than repeated cutting that takes plant energy to heal. Leave old growth unpruned over the winter to protect/insulate the central crown of the plant.

5. Provide protection. Respond to spring hard freeze warnings by covering tender plants with cloth or paper. Plastic is not advised. Cover the plant from top to soil level to trap heat radiating up from the soil.

Organic Strategies

Strategies 1, 2, 4 and 5 are strictly organic approaches. Using an appropriate organic fertilizer would be a viable organic approach to Strategy 3.

More images:

This ginkgo (Ginkgo) lost all of its leaves in the late spring freeze that occurred in 2007; the tree later put out all new leaves	Closer look at the frozen leaves on a ginkgo (Ginkgo) that lost all of its leaves during the late spring freeze that occurred in 2007; the tree later put all new leaves
Curled petioles on shadbush serviceberry (Amelanchier canadensis) possibly caused by the late, hard freeze in spring 2006; only this grove of serviceberries had curled petioles	Curled petioles on shadbush serviceberry (Amelanchier canadensis) possibly caused by the late, hard freeze in spring 2007; only this grove of serviceberries had curled petioles
A container wrapped in a fabric row cover to protect it from frost. Unfortunately, this will not help much because the cover needs to be secured to the ground to take advantage of soil warmth.	A blue tarp held down with pavers to protect a group of containers from frost damage. Unfortunately, to take advantage of soil warmth the covering should surround the container and be secured to the ground all the way around.
Row covers held down with rebar to protect tender vegetables from frost damage	Ice-coated branches are more susceptible to wind damage and breakage
Ice-coated branches are more susceptible to wind damage and breakage	Brown leaves on forsythia caused by late frost damage to forsythia
Damaged shoots on a forsythia branch due to late frost damage	The weight of snow or ice can split the canopy of an arborvitae (Thuja). Recovery may occur depending on the extent of the damage.
To prevent snow or ice from splitting the canopy of an arborvitae (Thuja) tie the crown together with nylon stockings when a storm is predicted and remove before spring.	Evergreens, in this case white pine (Pinus strobus) often suffer most from ice storms because they have more leaf surfaces to which the ice can cling.
Evergreens, in this case white pine (Pinus strobus) often suffer most from ice storms because they have more leaf surfaces to which the ice can cling.	River birches (Betula nigra) are particularly vulnerable to ice and snow damage.
River birches (Betula nigra) are particularly vulnerable to ice and snow damage.	Frost damage on hosta (Hosta)
Ice damage on arborvitae (Thuja)	Close-up of probable frost damage on redbud leaves (Cercis canadensis)
Probable frost damage on redbud leaves (Cercis canadensis); although similar, anthracnose is unlikely due to crinkled green leaf tissue	The shot holes on this hickory leaflet were probably caused by frost damage that occurred just as the leaves were unfurling
The weight of ice from an ice storm caused this tree to topple but the real damage occurred when the foundation was dug for the house on the right, cutting the tree's roots on that side	Branches broken from ice buildup
Snow buildup on a Japanese falsecypress (Chamaecyparis)	Snow buildup on a Japanese falsecypress (Chamaecyparis)
Sweet bay magnolia (Magnolia) damaged by ice	This breathable fabric draped around a pot shows one method of protecting tender plants when frost is predicted
Floating row covers are used to protect these vegetables from a late frost; note that material used is light weight and airy	When protecting plants from a frost, it is important to use a light weight material, such as, floating row covers, but the material must be secured to the ground to prevent it from blowing away and to take advantage of soil warmth.
Row covers are excellent for protecting heavy pots from frost. Unfortunately, to be effective the cover needs to be secured to the ground, not to the pot.	Damage to the upper right hosta leaf was caused by frost injury before the leaf had fully expanded.
Deformed, curled leaves on red oak (Quercus rubra) caused by frost damage as leaves were opening	Deformed, curled leaves on red oak (Quercus rubra) caused by frost damage as leaves were developing; upper leaf surfaces
Deformed, curled leaves on red oak (Quercus rubra) caused by frost damage as leaves were developing.; underside of leaves also showing a midrib tumor gall (Hymenoptera)	Slits in a hosta leaf created as the hosta leaf, injured by frost, expanded.
Open flowers on flowering quince (Chaenomeles) killed by a temperature of 11 degree F following an unseasonably warm period in February. Tight buds could still open normally.	Open flowers on flowering quince (Chaenomeles) killed by a temperature of 11 degrees F following an unseasonably warm period in February. Tight buds could still open normally.
Tomato transplant (Lycopersicon) set out too early and caught by a late freeze.	Strawberry fruit (Fragaria) frozen in late spring freeze
Frost damage to lettuce (Lactuca)	Ice damage on beauty bush (Kolkwitzia amabilis) caused by a leaky gutter
These sapcicles were formed from freezing sap flowing from a wound on a river birch (Betula nigra).	Heavy snowfall caused a row of arborvitae (Thuja occidentalis 'Klmeighteen' PATRIOT) to double over, nearly touching the ground.
Heavy snowfall caused a row of arborvitae (Thuja occidentalis 'Klmeighteen' PATRIOT) to double over, nearly touching the ground.	After the snow melted the row of arborvitae (Thuja occidentalis) are still split apart.
To repair arborvitae (Thuja) split apart by snow or ice, they must be tied back together until they mend. This could be done in early winter before damage occurs and removed again in spring.	Arborvitae (Thuja) split apart by snow or ice can be tied back together until they mend at which point the ties should be removed.
These arborvitae (Thuja) were split apart by a heavy snowfall, then tied back together until the following year at which point the ties were removed.	Bulb foliage coming up through the snow will not usually affect blooming. Damage can occur if flower buds have emerged.
Bulb foliage coming up through the snow will not usually affect blooming. No protection is required.	Frost flowers form when ribbons of ice extrude from long-stemmed plants, such as, Verbesina virginica, in autumn or early winter.
Frost flower on Verbesina virginica, one of the few plants that often produce frost flowers.	Frost flower on Verbesina virginica
The effect of cold injury on the flower bud of Hunka daffodil (Narcissus)	Frost protection for tomatoes (Lycopersicon). This length of plastic has open pockets that are filled with water and warmed by the sun.
A tomato plant (Lycopersicon) growing inside plastic cells filled with water and warmed by the sun.