Freeze damage in landscape plants
Problems caused by winter injury will show up slowly in spring and summer as plants begin to grow (or fail to grow). Buds are often more damaged than stems. A common symptom of freeze damage is loss of spring flowering, from buds being fully or partly frozen.
Rhododendron buds are often killed. If only partially frozen, the bud may unfold unevenly, looking disfigured. Bud freeze may ruin one season's flowers, but the plant can recover and flower normally the following year if not otherwise injured.
If plants are in a container and exposed to freezing air, the whole root system of the plant may be killed. Plants in containers are particularly apt to be killed in hard freezes, because the root systems don't recover from the cold injury.
A dwarf pine that would survive a hard freeze in the ground may be killed if it's in a container. Shallow root systems are more often affected than deep, well-established ones. Bark, especially bark on newly installed plants, can split if sun strikes when frozen. Newly-planted trees are often affected with bark splits, especially on the southwestern side where the sun hits.
Wrapping the trunk on a young tree through the first full growing season can help prevent cold-weather bark splits. Bark can also develop splits and cankers from frost damage. Graft unions are sensitive to cold injury.
When doing restorative prunning after winter damage, prune out only wood that is dead. Check for live wood by gently scraping through a tiny section of bark with a fingernail or a knife. Live cambium tissue will appear green or white; dead tissue is brown, dark brown, or even soggy. Start at the outer branch tips and move down toward the trunk. Younger twigs may be dead and older wood can be alive. Be patient; don't prune until spring growth shows the plant's response to cold.
If a plant has been injured, be sure it gets proper watering during summer. Mulch over the roots of plants with about 2 inches of a porous organic mulch. Fertilize lightly once the plants begin to grow.
Winter injury to plants depends on several variables, and is unpredictable. Keep notes as you observe your plants, and consider replacing any that have been killed with plants that are more hardy in your area.