Troubleshooting
Common Gladiolus problems — and how to fix them
Common Gladiolus (Gladiolus communis) 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.
Corm rot (Fusarium and Botrytis)
Soft, discoloured corms and collapsing plants indicate fungal rot, usually associated with wet, poorly draining soil. Lift corms at season end, discard any soft material, dust healthy corms with sulphur, and improve drainage before replanting.
Thrips (Thrips simplex)
Gladiolus thrips rasp leaf and petal tissue, causing silver streaking and deformed, speckled blooms. Treat with a systemic insecticide or spinosad spray and inspect corms for tiny insects before storage.
Overcrowding and reduced flowering
Corms multiply rapidly, and congested clumps produce fewer and smaller flower spikes. Lift and divide every 2–3 years in autumn, replanting the largest corms and discarding very small cormlets or keeping them to grow on separately.
Prevent common gladiolus problems before they start
Most common gladiolus issues are care-mismatch, not bad luck. Dial in the basics:
Looking for common gladiolus in general rather than its problems? Read the full common gladiolus care guide — light, water, soil and feeding.
Common Gladiolus problems — FAQ
Why is my common gladiolus corm rot (fusarium and botrytis)?
Soft, discoloured corms and collapsing plants indicate fungal rot, usually associated with wet, poorly draining soil. Lift corms at season end, discard any soft material, dust healthy corms with sulphur, and improve drainage before replanting.
Why is my common gladiolus thrips (thrips simplex)?
Gladiolus thrips rasp leaf and petal tissue, causing silver streaking and deformed, speckled blooms. Treat with a systemic insecticide or spinosad spray and inspect corms for tiny insects before storage.
Why is my common gladiolus overcrowding and reduced flowering?
Corms multiply rapidly, and congested clumps produce fewer and smaller flower spikes. Lift and divide every 2–3 years in autumn, replanting the largest corms and discarding very small cormlets or keeping them to grow on separately.