What's Wrong with My Plant?
by Don Janssen, Extension Educator
"What's Wrong with My Plant"?
What gardener hasn't said that at one time or another? Sometimes the answer is simple, but more often, it takes a bit of detective work to determine the cause of plant problems. To answer this question use a systematic approach to diagnose plant problems.
The first step is proper identification of the plant. This immediately reduces the number of potential problems by eliminating those that are specific to other types of plants. Reference books used for identification also may offer a list of typical problems for this species.
The next step is to define how the plant with the problem is different from a healthy plant. You may find insects munching foliage, leaves covered with powdery mildew or black moldy spots, or the bark gnawed off the stem of a small tree or shrub. In such instances, diagnosis is simple.
Quite often, however, the problem is not so clear-cut. The plant just isn't growing well, perhaps - leaves are small or sparse or off-colored. Perhaps a tree is losing its leaves or turning color when it shouldn't be, an expanse of lawn is turning brown or everything in a corner of the garden is wilting.
Examine every part of an affected plant, if you can. In trees, leaf symptoms often indicate damage to roots, trunk or branches. Then consider whether the problem is appearing in one plant, in multiple plants of the same species or in all the plants in a particular area. This can be an important clue to the source of the problem. Uniform damage to a mixed grouping of plants suggests a cultural or environmental cause - herbicide drift or pollution, perhaps - especially if symptoms occur all at once and don't progress. Damage on one type of plant or related plants only suggests a pest or disease organism that targets that plant family.
Another important part of diagnosis is a site history. When the problem was first noticed, where the plant is located - in a lawn, near a street, in a low-lying area, in the root zone of a black walnut tree, etc. - whether it's newly plants or established, whether construction or changing traffic patterns near the plant night have affected the root system, and whether pesticides or other chemicals (including deicing salt) have been used near the plant - all these are part of the total picture.
Unusual weather also needs to be considered. Often landscape ornamentals crushed by a heavy snow load don't show symptoms of damage until the next growing season by which time the homeowner may not make the connection. Hail, lightning, wind, ice, early or late frost, and excessive rain or drought all may play a role in plant problems.
Soil characteristics such as pH, fertility, drainage, compaction, contaminants and soil depth are other factors. A mismatch between the conditions the plant is adapted to and those of the planting site will leave plants struggling to survive and more susceptible to insect and disease attack.
Homeowners can be the cause of major plant problems. Cultural practices - watering (or failing to water), fertilizing, pruning, planting, mowing and mulching practices - can provide plants with the care they need or do them in in short order.
There are many ways to kill plants including selecting the wrong plant for the site, planting too deep or too shallow, letting roots dry our before planting, damaging stems with mowers and string trimmers, failing to water or overwatering, fertilizing too much or at the wrong time or not at all, girdling plants with guy wires, allowing roots or stems to be damaged by construction activities, or carelessly using herbicides around them, among others.
Once a plant has been weakened by environmental or cultural factors, it's more susceptible to insect and disease problems. So pest or disease problems may actually be symptoms of some underlying stress. Diagnosis is the systematic analysis of all these clues to arrive at a probable cause. The next question, of course, is what to do about it.
Sometimes plants die no matter what you do. Sometimes problems are cosmetic - leaf galls on maple trees are an example - and you don't need to do anything. With some problems, plants will die if we don't do something. The question then is whether the value of the plant justifies taking action to save it. 'Value' might be aesthetic or sentimental or economic. However you define 'valuable', the decision to treat or remove and replace a plant will be easier if it's based on information about the plant, the problem and the options.
For help with plant or pest identification, treatment recommendations, and information on plant selection, planting and care, contact your local Extension office.
(This resource was added September 2002 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement)
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