Spring is supposed to bring fresh new leaves and bright flowers, yet the opposite sometimes happens. Evergreens may show browning leaves or needles. On deciduous plants, new leaves may be yellowish, branches and twigs may die back, and growth is weak. Damage tends to be on one side of the plant rather than equally around the entire plant. In late summer, deciduous plants go into a dazzling display of color; except this occurs about a month too early. The problem is not a pest or disease, but salt damage from delicing salts.
Winter salts can hurt these plants.
The first step in controlling the problem is to stop using delicing salts yourself. Environmentally safe compounds are now available that, although more expensive than rock salt, are not harmful to plants. You can also use lawn fertilizer to melt accumulated ice. Since you cannot control what your city or town applies on nearby roads, hose down shrubs and trees near the road first thing in the spring. Also thoroughly water the ground at their feet so any salts will dissolve and be carried safely beyond the range of their roots. In areas where the problem is severe, consider planting a buffer zone of salt-resistant plants nearest the road. These plants will absorb the salt spray with little impact, protecting the plants inside your yard. Salt-tolerant plants need to be washed in the spring, as would other plants.
Some areas seem chronically dry. Even when rainfall has been abundant, plants suffer from scorched and brown leaf margins, wilt frequently, and branches and twigs die back. This problem is frequent with newly planted trees and shrubs as well as on slopes and in clay soils. It is caused by not enough water reaching the roots.
New transplants dry out more quickly and need more water than established plants. When planting, leave a basin (a ring of raised soil) around the root ball for the first year or so. This will help hold the water in place so it can soak in.
Clay soils hold water readily when damp but are hard to remoisten once they dry. Try watering slowly -- you don't want the water to simply run off into another section of the garden -- over a long period of time (up to 24 hours) to make sure the root ball is thoroughly moistened.
These conifers suffer from drought.
When established trees and shrubs stop growing after having done well for a long time, especially if the top branches die back and the leaves yellow and decrease in size, girdling is a possible cause. The roots of the plant wrap completely around the base, in effect, choking itself to death. Usually, the root is hidden from sight, and the cause of the problem is discovered only when the plant dies and is removed. Sometimes you can see the girdling root at the surface.
This problem can be prevented at planting time by removing or straightening any encircling roots. These types of roots are especially prevalent with container-grown plants. They should always be carefully inspected at planting time. A girdling root on an established plant, especially a large tree, can be difficult to remove and requires the assistance of an experienced arborist.
If slowly over a period of years growth is poor, leaves are yellowed, and dieback occurs, there could be many different causes. However, if various species all seem to be suffering from the same problem in the same spot, the likely problem is soil compaction. This problem is especially frequent after a new construction, such as a swimming pool or a building extension, is added to an established yard. Try pushing a bamboo stake into the ground at the spots where you suspect compaction might be occurring. If this is difficult or impossible to do, the soil is seriously compacted.
Compaction is difficult to correct around established plants, although verticutting or aerating may loosen up the soil in the surface area if that is where compaction has occurred. Machines can be rented or lawn specialists hired to do the job. Both verticutting and aerating will damage surface roots, but compaction is worse. If the plant is healthy, it will grow new roots.
It is better to prevent compaction by making sure the soil is well loosened at planting time. Thereafter, whenever heavy vehicles or machinery are used in the yard, make sure that a predetermined path is followed and that trees and shrubs requiring special protection are roped off. Do not allow constructors to pile soil or debris over the root area of plants, even for a short time. Such materials should always be carried off site.
Several types of winter injury can occur. The most common is due to the drying effects of cold winds (wind-burn). It is especially obvious on needled and broad-leaf evergreens. Windburn is best prevented by planting susceptible plants in a protected area. Another option is to set up burlap barriers to the windward side of these plants for the winter months. The problem can become worse if the plants do not receive generous amounts of water throughout the fall and winter seasons. If windburn is a recurring problem, try planting a windbreak.
Vertical cracks may form on the south side (north side in the Southern Hemisphere) of a trunk or branch in winter, especially on trees or shrubs with thin bark. These cracks provide a path for diseases and insects. The cause is sunscald: The bark heats up on a warm winter's day and freezes rapidly at night. Sunscald can be prevented by whitewashing the bark, which was formerly a popular treatment but not particularly aesthetic. Wrapping the trunk in a protective covering for the winter is another form of protection. Special spiral tubes are sold for this purpose (they also prevent damage by rodents), but simple aluminum foil is also effective.
Many animals can do much harm to your plants. Rodents such as field mice and voles are especially problematic in winter. They tunnel under the snow or through mulch or tall grass and nibble on soft young bark, especially the bark of fruit trees. Wrapping the trunk in 1/4-inch mesh hardware cloth or a commercial trunk protector will keep them away. Rabbits and hares nibble on tender buds in winter, causing setbacks and aesthetic damage to shrubs and young trees, but rarely permanent damage.
Although cute, this deer can wreck your tree's bark.
Deer are not as easily dissuaded and cause damage year-round. They are becoming increasingly common in suburban areas and are difficult to control. There are several commercial deer repellents. Although there have been several attempts to publish lists of plants deer do not like, they are often contradictory. Check with your county Cooperative Extension office to see if they have any suggestions for your area. The only truly effective deer repellant is an eight-foot-high fence.
Herbicides are made to eliminate plants. Not only can they damage or kill plants you want to get rid of but they can also harm plants you want to keep. Herbicides are of two types: selective, such as those used on lawns to kill broad-leaf weeds, and nonselective, such as those that kill all vegetation in driveways, sidewalks, patios, and the like. Either kind can harm woody plants if absorbed by the plant.
Always be extremely careful when applying such products. Apply only as recommended on the label. Heavy applications soak into the soil and can easily enter the roots. Avoid spraying on windy days or in extreme heat; herbicides can evaporate and travel to the foliage of nearby plants. Even "weed-and-feed" formulas can create fumes that are toxic to woody plants. The best rule is to put mulch underneath trees, shrubs, and vines so you will not need to apply pesticides.
Hopefully, your trees, shrubs, and vines are growing so abundantly that you need to prune them to keep them in shape. We'll show you how to prune in the next section.