To print: Select File and then Print from your browser's menu
Evergreen Problems: Cultural and Environmental
We love our evergreens and want them to not only survive, but thrive in our landscapes. Like all other living things, evergreens are affected by many different factors in their environment and by the care they receive. While we can't control everything, there are many things we can do to insure they do well. Environmental factors are those that occur in the whole area, not just in your yard or to your plants. Examples of environmental factors that affect the health and beauty of evergreens include weather extremes, wind exposure, excessive water or drought, air pollution and (because it is widely used on the roads) exposure to salt. Those things over which we have more control are the water we apply to the plants (either too much or too little), water quality, nutrition and soil pH. With careful cultural practices, we can also greatly reduce stresses caused by competition, poor pruning techniques and physical injury.
Environmental Problems
Temperature Extremes When temperatures change gradually, plants prepare themselves and are able to withstand our cold winters and variable summers. But sudden changes can do a lot of damage. When we go through a warm fall followed by a sudden severe onset of winter, plants that could normally withstand those temperatures can be hurt. And in spring, once new growth has begun to develop, even a light frost can cause damage. Many of the plants that are winter hardy in our climate rely on good snow cover to protect them from the cold; a winter with little or no snow can threaten these plants.
Wind Exposure Excessive wind can stress or damage plants by drawing too much moisture out of the foliage and twigs. No one has to look too far back to remember the incredible damaging power of the severe storms and tornadoes over the past few years. Even when the wind damage is not clearly visible, it can create cracks that are then potential sites for disease transmission, insect problems or rot.
Excessive Water or Drought Too much water for more than a day or two at a time is just as damaging as drought. Occasionally we go through an extended period of time when the ground is saturated. When this happens, the roots of plants can literally suffocate. On the other end of the spectrum, even mature, established plants can suffer from lack of water during even a short drought. The symptoms of both too much water and too little water are the same - roots are damaged and the foliage wilts.
Air Pollution Some varieties of evergreens are sensitive to the pollutants commonly found in the air in metropolitan or high traffic areas. Sensitive plants will show damage to their foliage, poor growth and susceptibility to other problems.
Salt Exposure If you have evergreens planted anywhere near a road or highway, salt exposure is a potential problem. As traffic goes by, a fine mist of salt spray is thrown into the air. On busy highways, salt damage can even occur 100 feet away up a slope. Salt damages plants by drawing water out of foliage and roots.
Cultural Problems
Too Little or Too Much Water At Bachman's, one of the most frequently asked question is about watering. There is no quick, easy answer. Factors involved include the size/age of the plant, the type of plant, how long it has been planted, the soil type, the weather conditions and the surrounding competition. The only generalization that is safe to make is that almost all plants will do well if they are kept slightly moist. Before watering, it is important to check to see if the soil is truly dry or just appears so on the surface.
Water Quality A combination of water with lots of salts and calcium and a high pH can cause plant problems. With many evergreens it is a matter of battling to keep the soil acid while the water that comes out of our hoses often has a pH as high as 8.0. For yard and garden use, filtering the salts and calcium out of the water is impractical, so the problem must be addressed by soil treatment.
Soil pH A high pH (alkaline) soil can greatly affect the health of those evergreens that require a low pH (acid) soil. Most of the soils in our area are alkaline. When a plant that requires acid soil is growing in alkaline soil, its ability to make use of the available nutrients is compromised. Because city water is usually alkaline, it is important to keep track of the soil pH around evergreens with regular soil tests and acidify the soil as needed.
Nutrition Evergreens are not heavy feeders and can do well for years on the nutrition available in average soils. But when we want to push them to grow as quickly as possible and keep them strong, extra nutrients are needed. As evergreens are primarily grown for their green foliage, nitrogen is the most important component of their nutritional needs. Making the right nutrients available to plants when and where they need them is important.
Competition Plants compete with each other for all their needs including light, water and nutrition. When plants are not getting the amount of light they need, they may not develop strong, healthy foliage. When they don't receive adequate water or nutrition, they are usually dwarfed as well as having weaker growth. Turf grasses are heavy feeders and very efficient competitors for the available water and nutrients and it is difficult for most evergreens to compete with them. Some varieties of evergreens (such as hemlocks) don't do well with lots of root competition from surrounding trees and shrubs. When plants are crowded, or when they have lots of competition, we need to be sure they are all getting the water and nutrients they need.
Physical Injury Statistically, people are the biggest enemy of trees or shrubs in the landscape. Injuries caused by mowing, tilling, digging, ditching, construction, climbing, pruning and such cause more damage in plants than any insect or disease. It is essential to consider plants as living things whose well-being can be threatened by our actions.
Additional Bachman's Information Sheets
Caring for Newly Planted Plants
Pruning Evergreens
Evergreen Trees -- Evergreen Shrubs
The Right Evergreen for the Right Site
Understanding Your Soil
Acidifying Soil -- Soil pH
Evergreen Problems: Insects
Evergreen Problems: Diseases
©Bachman's 2007