Q.Holly Hock & Rust
What can I do about the rust stains on the holly hock?
Certified GKH Gardening Expert
This will be a fungal infection present in the soil. Usually hollyhocks are short lived, and within a couple of years, new seedlings have grown into mature plants again. Treating the plant itself is not of much use.
You can treat the soil, however. Use DOLOMITIC LIME and WETTABLE SULFUR according to all packaging instructions to treat the area. This will help kill off anything lurking in the soil, as well as condition it back to a proper state.
This article will help you with the care of hollyhocks: https://www.gardeningknowhow.com/ornamental/flowers/hollyhock/tips-on-hollyhocks-growing-hollyhocks-successfully.htm