Troubleshooting
Big-Flowered Catmint problems — and how to fix them
Big-Flowered Catmint (Nepeta grandiflora) 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.
Stem flop in windy sites
Tall stems can topple without support. Insert pea-stick supports in spring before stems exceed 30 cm. Choose a sheltered position or stake with grow-through rings.
Powdery mildew in late season
Can affect foliage after the main flush. Cut stems back to 15–20 cm post-bloom; fresh foliage emerging in autumn is typically mildew-free. Good plant spacing helps.
Self-seeding
Plants may self-seed prolifically. Deadhead promptly after bloom to limit unwanted seedlings, or allow a few to naturalise in wilder garden areas.
Prevent big-flowered catmint problems before they start
Most big-flowered catmint issues are care-mismatch, not bad luck. Dial in the basics:
Big-Flowered Catmint problems — FAQ
Why is my big-flowered catmint stem flop in windy sites?
Tall stems can topple without support. Insert pea-stick supports in spring before stems exceed 30 cm. Choose a sheltered position or stake with grow-through rings.
Why is my big-flowered catmint powdery mildew in late season?
Can affect foliage after the main flush. Cut stems back to 15–20 cm post-bloom; fresh foliage emerging in autumn is typically mildew-free. Good plant spacing helps.
Why is my big-flowered catmint self-seeding?
Plants may self-seed prolifically. Deadhead promptly after bloom to limit unwanted seedlings, or allow a few to naturalise in wilder garden areas.