Troubleshooting
Long-leaved speedwell problems — and how to fix them
Long-leaved speedwell (Veronica longifolia) 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.
Powdery mildew
Grey-white fungal coating on leaves in warm, humid conditions with poor air circulation. Space plants adequately, avoid overhead watering in the evening, and remove affected foliage promptly.
Vine weevil damage
Adults notch leaf margins; larvae eat roots, causing sudden wilting. Apply biological control (Steinernema kraussei nematodes) to moist soil in late summer or use a licensed vine-weevil drench.
Flopping stems
Tall forms may need support in exposed or richly fertilised positions. Insert grow-through supports or pea sticks in spring before stems reach 30 cm, or deadhead after the first flush to encourage sturdier repeat spikes.
Prevent long-leaved speedwell problems before they start
Most long-leaved speedwell issues are care-mismatch, not bad luck. Dial in the basics:
Looking for long-leaved speedwell in general rather than its problems? Read the full long-leaved speedwell care guide — light, water, soil and feeding.
Long-leaved speedwell problems — FAQ
Why is my long-leaved speedwell powdery mildew?
Grey-white fungal coating on leaves in warm, humid conditions with poor air circulation. Space plants adequately, avoid overhead watering in the evening, and remove affected foliage promptly.
Why is my long-leaved speedwell vine weevil damage?
Adults notch leaf margins; larvae eat roots, causing sudden wilting. Apply biological control (Steinernema kraussei nematodes) to moist soil in late summer or use a licensed vine-weevil drench.
Why is my long-leaved speedwell flopping stems?
Tall forms may need support in exposed or richly fertilised positions. Insert grow-through supports or pea sticks in spring before stems reach 30 cm, or deadhead after the first flush to encourage sturdier repeat spikes.