Southern favorites, crepe myrtles (Lagerstroemia indica), produce showy, long-lasting summer blooms. Native to Asia, these shrubs or tiny trees develop in U.S. Department of Agriculture plant hardiness zones 7 through 9. Although typically trouble-free plants, crepe myrtles sometimes start sporting green growth on the bark of trunks, twigs or branches. This green stuff is probably a lichen, a harmless organism that doesn’t damage plants. If you don’t like the expression of the lichen, it is possible to remove it.
About Lichens
Lichens are unusual plantlike organisms that consist of both fungi and algae growing together in a single body. The fungi and algae like a beneficial, symbiotic relationship, with the latter producing food through photosynthesis and the former providing vitamins, water and a protective structure. Working collectively, those organisms make it possible for lichens to prosper in a number of the Earth’s harshest climates. Lichens appear as well-adhered, green to grayish-green, crusty, scaly, feathery or leafy growths on a vast variety of surfaces, but especially thrive on unhealthy plants. Though they appear on declining crepe myrtles, the organisms themselves are not accountable for the plants’ lack of vigor. Ailing shrubs and trees usually have thinned canopies and fewer leaves, allowing more sunlight to reach the bark. The lichens simply make the most of these sunny spots.
Removing Lichens
You shouldn’t fret too much about lichens growing on crepe myrtle bark. The lichens are harmless and the myrtle bark peels off every year. The lichens should come off with the peeling bark from summertime. If you truly find the green lichens unattractive, try gently scrubbing the affected bark with a stiff steel brush. Wait until after a rain or bend down the bark prior to scrubbing to help soften the lichen.
Chemical Lichen Control
Applying herbicidal soaps especially designed to kill lichens, algae and mosses will help to control the green stuff growing on your own crepe myrtles. The fatty acids in the potassium salts quickly kill lichens without damaging or discoloring the bark. Herbicidal soaps come in a variety of formats, including easy-to-use, ready-to-spray bottles that you hook up to a garden hose. Carefully read and follow the directions and safety precautions on the manufacturer’s label because instructions do vary. One product recommends first wetting down the affected bark with water and then saturating the lichens with the product. Wash the treated bark with 1 gallon of water approximately 15 minutes after application, but avoid heavy watering for at least six hours after therapy. Reapply the solution if it rains within 24 hours of program.
A Few Factors
Although the lichens will turn brown and die within a few days of the herbicidal soap therapy, the growth may stay on your plant until the wind blows it away or rain rinses it from the bark. Gently rub the dead lichens with a moist wire brush to remove the development in the crepe myrtle. Although nontoxic to humans and creatures, herbicidal soaps may nevertheless cause skin and eye irritation. Prevent exposure by wearing eye goggles, a face mask, waterproof gloves, long sleeves, shoes with heels and pants. Spray herbicidal soaps only when the weather is calm and rain isn’t expected for at least 24 hours after treatment. Implement in late afternoon or early evening in warm weather to avoid burning the leaf. Don’t allow pets or family members into the treatment area until the spray completely dries.