Q: I’m having a problem with my azaleas. They seem to have lichens on the trunk. I cut them back as much as possible, fertilized and sprayed with liquid Sevin but they don’t seem to be getting any better.

I hate to see them die, which they are slowly doing.

A: I think you should like your lichens. Azaleas and older trees of many species often have gray, flaky lichens growing on their limbs.

Interestingly, a lichen is a “sandwich” made of algae in the center and fungus on the outside. The algae makes food from sunlight and air; the fungus protects the algae and supplies moisture. They live together symbiotically.

Since lichens are almost always found on weak plants, do lichens cause the plants to become sick? No. In fact, lichens are totally harmless and in no way responsible for the poor health of any tree or shrub. They are simply indicators of the infirm health of the plant.

As a woody plant loses vigor, the number and size of its leaves gradually decreases. This allows more sunlight on the trunks and branches. As soon as enough light is available on the stems, lichens will begin to colonize.

Lichens can be brushed off the plant with a stiff brush but Sevin won’t affect them. Unless the true cause of decline is corrected, lichens will reappear.

Are your azaleas growing in dense shade? Do they get enough water in the summer? Maybe the best thing to do would be to prune them to twelve inches tall next March and let them grow a better canopy of leaves.

If a plant is helped to become more healthy, less sunlight will strike the limbs and trunk. Lichens will then gradually disappear.