Pocket BotanistSymptoms by part
Leaves
Small, raised, reddish brown or orange pustules appear on the undersides of the leaves, often accompanied by yellow or light brown spots on the top surface.
Causes
- High humidity around the foliage
- Poor air circulation between plants
- Overhead watering that keeps leaves wet for long periods
- Crowded planting conditions
Could be confused with
- Leaf spot diseases · Leaf spots are usually flat and lack the dusty, raised pustules characteristic of rust.
- Natural leaf variegation · Variegation follows a consistent pattern across the leaf and does not feature raised, powdery bumps.
Treatment
- Prune away and destroy all infected leaves as soon as you spot the pustules to stop the spread.
- Clean your pruning shears with rubbing alcohol between every cut to avoid moving the fungus to healthy parts of the plant.
- Thin out neighboring plants to improve airflow and reduce humidity around the base of the coral bells.
- Apply potassium bicarbonate to the foliage to alter the pH and inhibit fungal growth, follow the label.
Without chemicals
- Remove and dispose of all fallen leaves from the soil surface to prevent spores from overwintering.
- Switch to drip irrigation or water at the base of the plant to keep the foliage dry.
- Space plants further apart to ensure good air movement.
Chemical options
- Potassium bicarbonate, spray on leaves to create an unfavorable environment for the fungus, follow the label.
Preventing it
- Water only at the soil level, never overhead.
- Ensure plants have enough space for air to circulate freely.
- Keep the area around the base of the plant clear of debris.
- Choose planting sites with good morning sun to help dry the dew off the leaves quickly.
Season
The warm growing season, especially during periods of high humidity or frequent rain.
Spread risk
Moderate
Severity
Moderate
When to act
Act as soon as you see the first orange pustules on the undersides of the leaves. If the entire plant becomes covered and weak despite your efforts, remove and discard the plant to protect your other specimens.
Think it's Heuchera Rust?
This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.
Questions people ask
- Will my coral bells recover after I remove the infected leaves?
- Yes, if you catch the infection early and improve the airflow, the plant will typically push out healthy new growth.
- Can I compost the infected leaves?
- No, it is best to bag and discard infected leaves in the trash to prevent the fungal spores from spreading throughout your garden.
Plants it affects
This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.