Answer: Hollyhock rust is a very common fungal disease. It begins with yellow or orange spots with red centers on the top side of the leaf, along with brown pin-head sized dots on the underside of the leaf. Eventually gray pustules form on the underside of the leaf, and all the spots run together, killing big areas of leaf tissue.
Hollyhock rust overwinters on the basal leaves and old stems of the plant. In the fall, after killing frosts, remove and destroy the old leaves and stems. During the growing season you can remove and destroy infected leaves. Disturbing plants while the leaves are wet spreads the disease, so allow plants to dry before working around them.
Other cultural practices that keep hollyhocks healthy include growing them in full sun, in rich moist soil and making sure they have good air circulation. Another tip is to grow them in the back of the garden with shorter plants in front of them to conceal the damage. Some gardeners grow them as biennials, starting new plants every year, and removing them after they flower in their second season. This keeps diseases from building up on older, weaker plants.
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