How to Care for Liatris

Remove weeds from within a 1-foot radius of the liatris. Weeds compete with the plant for nutrients and water. This competition may decrease the amount and size of the plant's flowers.

Water the liatris to keep the roots slightly moist. Stick a screwdriver into the soil at the plant's dripline to determine when it's time to water. Overwatering may kill the plant, while insufficient water places it under stress, which leads to disease. Water the liatris at the soil, not from overhead.

Fertilize liatris four times during the season. Apply the first application three weeks after planting, and reapply every 10 days until you've provided four applications. Use a 20-20-20 fertilizer at the rate suggested on the label.

Check the liatris periodically for signs of pest infestations. Common pests on the plant include thrips, aphids and whiteflies. Aphids can generally be washed off the plant with a strong burst of water from the hose. If required, use an insecticide containing carbaryl or malathion or use an insecticidal soap spray, suggests horticulture specialists with Kansas State University.

Avoid fungal disease by not crowding the plants, watering early in the day and keeping the bed free of debris. Use a fungicide spray at label rates to control powdery mildew -- a fungal disease that looks like a white powder on the foliage.