The recent snowstorms, with the temperatures plunging to single digits or even below, remind us of garden tasks yet unfinished. The severe damage to many plants last winter should give us ample motivation to do all we can to protect tender plants. The protection we can provide is somewhat limited but is very important. It requires a little effort to help the plants come through the winter in good shape.
Roses and other perennial plants require mulching. Mulches are often thought to keep plants from freezing, but actually the reverse is true. Mulches are designed to keep the ground frozen. Mulches should not be applied until the weather has turned quite cold and the soils are frozen. Many times it is not the cold temperature that destroys these plants, but the alternating freezing and thawing of the soil. As ice forms and thaws in wet soils, it expands and contracts. This expansion and contraction is called heaving. It can sever all of the small roots, and the plants die because they have been uprooted through this natural freezing and thawing of the soil.Most soils are now very cold or frozen, and it is a good time to protect those roses. If you haven't already done so, trim the roses to 3 or 4 feet. This prevents additional snow breakage and whipping in the wind. Next, pile a cone of soil, bark chips, or other substantial mulch material around the center of the plant. This should cover the canes about 12 inches deep to protect them. Gardeners who lost roses last year realize the importance of protecting those growing points. Many roses were killed by the extremely cold temperatures, and the only thing that protected many others was a snow layer. Don't depend on nature this year; add some mulch to protect your valuable plantings. Perennial beds need a lighter mulch applied over the top of the plants and most other woody plants also benefit from a mulch.
Fruit trees also require some finishing touches to put them to sleep. Young fruit trees, particularly the stone fruit trees, should have the trunks protected from southwest winter injury. This injury occurs when the sun shines on the dark trunk during the winter and warms it well above the ambient air temperature. This causes the dormant cells to start growing. Trees produce no heat, and they quickly drop to the outside temperature when the sun goes down. These rapid and extreme fluctuations in bark temperature cause the cells to die and the bark to peel away from the trunk.
Wrapping the trees with a white tree wrap or with a tree guard effectively keeps the bark temperature from rising during the winter sunshine. Painting the tree trunk with a white, latex paint or standing a board as a shade for the trunk will also work effectively.
In addition to the stone fruit trees, newly planted lindens, maples, honey locusts and other thin-barked trees will benefit from this treatment. Tree wraps should be left on the tree until temperatures moderate, generally in late February.
Don't forget to wrap up the arborvitaes and other tall upright evergreens. As I drive around the valley, I see many that have already been pulled down by the snow. If snow remains on the branches, shake it off and wrap the tree with burlap strips or another tree wrap.
The weather conditions have been conducive to the development of coryneum blight on stone fruit trees. Fall moisture is a major factor in the spread of this disease, particularly in peaches. Control of this disease has been complicated by the early freezing of the leaves and the failure of these leaves to drop. Since this fungus invades through the bud scale scar, (the opening left when the leaf falls from the branch), it has been difficult to know when to spray. Most of the leaves have now fallen from my trees and hopefully have fallen from yours. Spray the trees with Daconil (chlorothalanil) or with one of the fixed coppers. These sprays are available at any nursery. Sprays reduce the amount of dead twigs and the number of dead buds next spring.
Even though winter is not the most pleasant time to be out in the garden, a couple of hours spent on these tasks can prevent serious damage to your plants this winter. Before you hibernate this winter, make one last effort to make sure you have done all you should to protect your plants. Whatever Mother Nature has in store for them in the next few months, you'll be able to sit in front of a cozy fire with a clear conscience.
- JOIN ME THIS SATURDAY on the KSL Radio Greenhouse Show from 7-10 a.m. Alex Shigo, one of the world's most prominent authorities on tree growth, will join me and help answer questions on tree health.