Troubleshooting
Sweet William problems — and how to fix them
Sweet William (Dianthus barbatus) 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.
Crown rot
Caused by waterlogged soil or poor drainage; plants collapse at the base and fail to overwinter. Grow in sharply drained soil, raise beds if needed, and avoid planting in depressions where water pools. Never allow pots to sit in saucers of water.
Dianthus rust (Puccinia arenariae)
Orange-brown pustules on leaves and stems, particularly in humid conditions. Remove and destroy affected leaves promptly, improve air circulation by spacing plants adequately, and apply a fungicide containing myclobutanil or triticonazole at early signs.
Aphids and tortrix moth
Aphids cluster on new growth, causing distortion, while tortrix moth caterpillars roll and tie leaves with silk. Check plants regularly from spring; remove caterpillars by hand and treat aphid colonies with insecticidal soap or a pyrethrin-based spray.
Prevent sweet william problems before they start
Most sweet william issues are care-mismatch, not bad luck. Dial in the basics:
Looking for sweet william in general rather than its problems? Read the full sweet william care guide — light, water, soil and feeding.
Sweet William problems — FAQ
Why is my sweet william crown rot?
Caused by waterlogged soil or poor drainage; plants collapse at the base and fail to overwinter. Grow in sharply drained soil, raise beds if needed, and avoid planting in depressions where water pools. Never allow pots to sit in saucers of water.
Why is my sweet william dianthus rust (puccinia arenariae)?
Orange-brown pustules on leaves and stems, particularly in humid conditions. Remove and destroy affected leaves promptly, improve air circulation by spacing plants adequately, and apply a fungicide containing myclobutanil or triticonazole at early signs.
Why is my sweet william aphids and tortrix moth?
Aphids cluster on new growth, causing distortion, while tortrix moth caterpillars roll and tie leaves with silk. Check plants regularly from spring; remove caterpillars by hand and treat aphid colonies with insecticidal soap or a pyrethrin-based spray.