Filed under: Arborific Articles, Tips & Tricks. Tagged as: Plant Health Care, Tree pruning.
This morning the upper Willamette Valley, USA experienced our first light frost of the season. Symptoms of frost injury include wilting, blackening or browning of leaves, and even young stems. Sometimes only the leaf magins or a few spots on the inside of the leaf, will turn brown. Frost damage often looks a lot like the sun scald, that happens in the summer. The stems or trunks of young trees will sometimes split. These splits will usually be located on the south or west sides of the plants. Frost cracks can even occur on plants that are cold hardy; such as Japanese Maples, fruit trees, both flowering and fruit bearing, if they have not “hardened off” completely. In the spring, with late frosts, the new buds of flowers will frost and turn black or brown, and die.
In our valley, we rarely have hard enough frosts to freeze the ground and root systems. However, trees and shrubs growing in containers can be very susceptible to root damage. Also, newly planted or transplanted trees and shrubs that have not had enough time to expand and bury their roots can be susceptable. If a frost or freeze lasts long enough and even normally hardy plants can be killed. This is often not noticed until spring, when little or no new growth takes place on top of the plant.
Some plants like Rhododendrons and azaleas will often look damaged, with curling, drooping leaves, when it is just their normal reaction to cold weather. Arborvitae and other cedar will turn a sort of copper color in the winter when they are dormant. Both conditions come back to their normal healthy green growing habits as spring comes back.
WHAT YOU CAN DO:
• Plant susceptible or marginal plants in the warm spots in the garden. These can be next to the foundation of the house, near brick or concrete walls, benches or sheds, or under decks and over hangs of the house. Southern facing slopes and southwestern areas of gardens also tend to get a warmer during the day, and may be less prone to frost than other areas.
• Discontinue fertilizing in late summer or early fall, so that there is no new foliage is on the plant when temperatures drop. Older leaves are much tougher when it comes to surviving a frost. Fertilizing later in the fall is excellent for giving strength and endurance to root systems.
• Bring potted plants under a cover, or into a green house or garage at the first signs of frost. If they are already in a protected location, wrap the pots with loose burlap or other materiel.
• Keep plants well watered. Frost injury occurs by drawing moisture from the leaf tissue. The damage from dehydration will be less if the plant is well watered before hand.
• Mulches can insulate against some fluctuating soil temperatures. In the spring, they can guard against too much daytime warming that could activate early growth that will be damaged by cold weather.
• If there is a chance of freezing rain in the forecast, cover smaller plants with cloth; sheets or blankets or paper to insulate. Be sure to uncover in the morning or when the freezing rain has passed. Otherwise the warmth is likely to cause the plant to break dormancy to soon.
• Wait until spring to do any pruning of suspected frost damaged trees or shrubs. As spring weather brings on new growth, call True Care Inc. Tree Service for your pruning needs.