When diagnosing a plant problem, you must sometimes be part doctor, part coroner, part private detective and part historian. Each of these professions asks questions to help them come up with the correct answer to a problem.

In medical terms there are signs and symptoms. A sign is an actual part of the living organism that may be causing the problem, or direct evidence. You don't have to see the organism itself to know what it is. The droppings from deer, slime trails from slugs, insect eggs, insect pupa or cocoon, and mushrooms in the lawn are all signs of problems.

Symptoms are the altered appearance of the organism affected. Changes in color, dying leaves or other plant parts, galls, sunken or swollen tissue are all symptoms. Many diseases have specific symptoms on specific plant species.

Plants may have more than one symptom and may have a combination of signs and symptoms. Of course a plant may have more than one problem at the same time giving it more than one sign and symptom at the same time. Very often the most noticeable sign or symptom is not the most serious problem the plant is experiencing.

After looking at the medical issues, we need to look at the historical time line of when the signs and symptoms appeared and are they continuing to develop. Are they linked to any changes in the environment? What level of landscape maintenance has been applied and when? The detective in us will start looking for signs and symptoms in other unrelated plants, across this landscape and the neighbors. These are all general principles, but how do we specifically diagnose a plant's problem?

First, we must start by correctly identifying the plant. Knowing just the common name is often not enough, because many plants can have the same or similar names. Many plant families have specific problems that belong just to it, besides the general problems common to all plants. We must also know what the plant is supposed to look like when it is healthy. You can't know if it looks sick unless you know what it looks like when it is not sick.

Second, we must really look at the whole plant and its surroundings. Novices often get stuck looking at the most noticeable symptom and miss the true cause of that symptom. For instance, a wilting plant may need water. Or, it could have so much water that the roots are dying. Upon close inspection it may be that the trunk has been damaged by insects or a string trimmer, thus not letting the water flow between the roots and the top.

Plant symptoms often have a specific point at which the damage starts. Follow the symptoms back to their starting point lower on the plant where healthy and sick tissue meet to see if a sign is visible. Are the symptoms continuing to develop on more parts of the plant?

Third, is the plant growing in the proper conditions for that plant? Are any of the environmental factors, such as altitude, humidity, light, soil pH, soil moisture and temperature, not in the plant's thrive zone? How long has the plant been in this location? Have any of these factors changed recently, such as removing a tree that provided shade? What kinds of chemicals have been used in landscape maintenance, pool maintenance or house work?

Fourth, do the signs and symptoms appear on neighboring plants? Are more plants developing symptoms? Are these plants in the same family or are they unrelated? Most insect and disease problems are limited to specific plant families. If the signs and symptoms appear on more than one plant family, an environmental or manmade cause is more likely. One major exception to this rule is the Japanese beetle that eats the leaves on hundreds of plant species across dozens of plant families.

In the last three steps we asked if there were changes over time. Many insect and disease problems don't last very long. Some environmental problems such as a killing freeze are short, but depending on the life-cycle stage the plant is in, the symptoms may show up within hours or not show up for weeks.

Fifth, after looking at all of the answers to the first four steps, what patterns have developed? Insects often eat holes or parts of leaves. Many diseases create colored and dead circular spots on leaves. Environmental problems tend to affect the whole plant at once. Chemical damage tends to cause leaves and stems to curl and become distorted. Uniform symptoms on several plant families will tend to indicate environmental problems. With a little bit of practice, you will start noticing the patterns.

Email questions to Jeff Rugg at [email protected]. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.