Rust on Hollyhocks: Managing the Most Common Hollyhock Disease

Hollyhock rust is so ubiquitous in the eastern US that experienced gardeners often treat it as an inherent feature of growing hollyhocks rather than a disease to be managed. That fatalism is understandable -- *Puccinia malvacearum* is nearly impossible to prevent entirely in humid climates -- but.

Hollyhock rust is so ubiquitous in the eastern US that experienced gardeners often treat it as an inherent feature of growing hollyhocks rather than a disease to be managed. That fatalism is understandable — Puccinia malvacearum is nearly impossible to prevent entirely in humid climates — but management does matter. Well-managed hollyhocks with early rust intervention bloom reliably and maintain attractive foliage through June. Unmanaged hollyhocks often look defoliated by July.

I don't grow hollyhocks at my Long Island property currently, so this guide draws on Extension research. They are common in zone 7a and perform well here when rust is managed.

Pathogen Biology

Per Missouri Botanical Garden, Puccinia malvacearum is one of the few rust fungi that completes its entire life cycle on a single host (autoecious rust), rather than requiring two different plant species. This means:

• No alternate host is required for the rust to overwinter and reinfect
• The rust persists wherever hollyhocks (and related mallows — Alcea, Malva, Malvastrum) are growing
• Eliminating the disease entirely would require eliminating all hollyhocks and related mallows from the area, which is not practical in most neighborhoods

P. malvacearum overwinters as teliospores on infected plant tissue, plant debris, and dormant stem tissue. In spring, these germinate to produce basidiospores that initiate new infections. Season-long spread occurs via urediniospores.