Troubleshooting
Hemp-leaved Marshmallow problems — and how to fix them
Hemp-leaved Marshmallow (Althaea cannabina) is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Mallow rust (Puccinia malvacearum)
As with other Malvaceae, rust disease produces orange pustules on leaves. Space plants well for airflow, remove infected material promptly, and apply sulphur-based fungicide if needed.
Root rot in wet soils
The taproot rots rapidly in waterlogged or poorly draining soils. Plant in raised beds or well-amended ground; do not overwater.
Flea beetles
Small round holes in leaves indicate flea beetle feeding. Damage is cosmetic on established plants. Protect seedlings with fleece or sticky traps.
Prevent hemp-leaved marshmallow problems before they start
Most hemp-leaved marshmallow issues are care-mismatch, not bad luck. Dial in the basics:
Hemp-leaved Marshmallow problems — FAQ
Why is my hemp-leaved marshmallow mallow rust (puccinia malvacearum)?
As with other Malvaceae, rust disease produces orange pustules on leaves. Space plants well for airflow, remove infected material promptly, and apply sulphur-based fungicide if needed.
Why is my hemp-leaved marshmallow root rot in wet soils?
The taproot rots rapidly in waterlogged or poorly draining soils. Plant in raised beds or well-amended ground; do not overwater.
Why is my hemp-leaved marshmallow flea beetles?
Small round holes in leaves indicate flea beetle feeding. Damage is cosmetic on established plants. Protect seedlings with fleece or sticky traps.