Experts and BHG readers answer.
rust on hollyhocks
Sadly, rust is often a fact of life with hollyhocks. Ways to combat rust is to make sure the plants have plenty of air circulation so don't plant them too close together and to remove all infected foliage and old, diseased foliage from the garden as they appear. However, the only surefire method is to spray the plants with a garden fungicide every 7 to 10 days through the spring and early summer. The rust won't kill your plants or prevent them from flowering, but it does make them look pretty ratty. Remember, however, that hollyhocks are biennial, which means they grow one year, then come back and grow and bloom the second year and die. It often looks like they are perennial in nature because they reseed themselves so thickly. So, once the plant blooms it's not worth spraying or fussing with. In my garden, I just live with the problem since I don't like using fungicides.