By Paula Flynn
Extension Plant Pathology
Iowa State University
Its a popular tradition to make a few resolutions for the New Year. A common theme of these resolutions is to live healthier. The list typically includes eating more fruits and vegetables, exercising, and fitting in more time for fun and relaxation. This list can get a little boring when used year after year, so it might be time to add a new, green twist. Add on a few actions that can help improve the overall health of the plants in your yard and garden. The trees that bring shade, the flowers that color the front doorstep, and the juicy tomatoes that are fun to gather all add to the quality of our surroundings.
Plant health problems are caused by a variety of organisms -- fungi, bacteria, viruses, and microscopic worms, called nematodes are a few. Adverse weather conditions and poor plant care can also prevent plants from growing well, blooming, or producing fruit. The common plant problems of 2004 illustrate some simple practices that can be used to encourage healthy plant growth in 2005.
Scab on crabapple. Most crabapples start the season magnificently, with many eye-catching, colorful blooms. However, by midseason, some crabapples lose their leaves and look bare. A close look at fallen leaves shows scattered black spots and a sickly yellow color. The culprit is a fungus that invades the leaves and causes a disease commonly known as scab. One control measure for this disease is to protect the leaves as they emerge in the spring with a fungicide. Sprays can be costly, a chore to apply, and must be repeated. A much simpler solution for this problem is to plant a scab-resistant crabapple variety. There are many different scab-resistant crabapples available.
As a general practice, do some homework before buying plants. Check descriptions in garden catalogs. More and more disease-resistant plants are becoming available, not only for trees, but also fruits, vegetables, and flowers. Avoiding diseases by using resistant plants is much simpler and cheaper than managing diseases after they appear.
Dutch elm disease. Our native elm trees began disappearing from the countryside in the 1930s when the Dutch elm disease fungus was introduced into this country. It has been estimated that 95 percent of the American elm trees in cities died from this disease. However, there are still a few elms scattered in our landscapes. Unfortunately, the Dutch elm disease fungus is also still present, and continues to kill elm trees. Several strategies are required to manage this disease. When practical, remove diseased branches or entire trees that are diseased to prevent further spread of the problem to similar plants.
In addition, since most diseases tend to be fairly specific to a plant or group of closely related plants, it is a good idea to plant a diversity of plant species. Recall that many neighborhood streets were once lined with elm trees. When Dutch elm disease moved through, all of the American elms were lost. By planting an assortment of plant species, a widespread loss can be avoided.
Trunk troubles. People, not microscopic microorganisms, are to blame for two common problems that cause trees to grow poorly and decline. You dont have to look far to find trees and shrubs that have sustained mower blight. When careless mowing damages bark, wood decay fungi may enter, as well as harmful insects. Bark not only serves to protect the tree, but is also a vital part of the food and water transport system for the tree. A simple, plant-healthy solution is to protect the base of the tree with mulch. Mulching around plants provides many benefits in addition to protection. It reduces weed or turfgrass competition, provides organic matter as it breaks down, buffers the soil temperature from extreme changes, helps retain moisture, and keeps mowers away from vulnerable tree trunks.
The second common cause of trunk trouble results from planting the tree or shrub in the ground too deeply. Before planting, take time to find the junction between the roots and the base of the trunk. In simple terms, the roots should be buried just below the soil surface and the trunk should remain above the ground. Soil sometimes is piled too high on the trunk, resulting in either a quick death or a slow decline over a period of years.
Just as there are many ways to improve our health, there are many ways to improve plant health. By doing some homework on the basic needs of your plants, you will be much more likely to meet these needs. Finally, to meet that goal of more exercise, take frequent walks around in your yard and garden to catch any plant problems early.
Best wishes for a plant-healthy New Year.
Editors: No photos are available for this week's garden column.