Curling Leaves on Coleus

Signs

• Curling leaves is a sign of downy mildew. The mildew spores develop on the undersides of the leaves, so look for tiny spots that indicate sporification, or white, grayish fuzz. Leaves may also drop from the plant or may have black spots.

Prevention

• Check transplants thoroughly before bringing them home to your garden. Avoid plants with disfigured leaves or leaves with any kind of spots. Lift the leaves and check the undersides for spots as well. Downy mildew is notoriously difficult to diagnose before symptoms have already damaged the plant.

Control

• If you notice plants in your garden or window boxes that you have identified as having downy mildew, remove them immediately. Wrap a plastic bag around the infected plants to avoid disturbing and dispersing the spores. Seal the bags and throw them in the trash. If the remaining plants seem to be unaffected, help them out by increasing air circulation and making sure the soil isn't too wet. If it is, hold off on the water until the soil dries out a bit. Fungicides for downy mildew are currently only available for use by professionals.

Resistant Varieties

• According to Mary Hausbeck of Mississippi State University, the following coleus cultivars have shown resistance to downy mildew: Fairway Mosaic, Fairway Red Velvet, Wizard Velvet Red, Fairway Salmon Rose and Fairway Rose.