Rust fungus is the curse of hollyhocks. The undersides of the leaves are often peppered with bright yellow or orange-red rust spots with corresponding beige-yellow splodges on the upper surface. Eventually, it affects the whole plant, with leaves starting to fall away from the base. In severe cases the stem becomes infected too, and the whole plant may die.
Orange-brown spots on foliage and stems. Leaves may die and drop from plants, weakening the plant and resulting in death in extreme cases.
Find it on
Remove infected leaves from plants as soon as the fungus is seen. In winter, when the hollyhock dies down, clear away any infected leaves as they will harbour the fungal infection. Weeds such as common mallow, which are related to hollyhocks, also harbour rust so pull them out if they appear in the garden.
Every two weeks from early spring onwards spray plants with a systemic action fungicide.