Deadhead plants regularly to encourage more flowering. Blanket flowers are often relatively short-lived. Cutting back clumps to 6 inches in late summer often increases their chances of winter survival. You can also keep your plants vigorous by dividing them every 2-3 years in spring or early fall. Water newly set out or divided plants regularly until they become established. Blanket flowers have few insect or disease problems. Watch for aphids and leafhoppers that can spread a virus-like disease called aster yellows. Control insects with insecticidal soap, if needed, and destroy any plants that are stunted with flowers that remain green, as these are infected with aster yellows.