Troubleshooting
Nettleleaf Giant Hyssop problems — and how to fix them
Nettleleaf Giant Hyssop (Agastache urticifolia) 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.
Flopping or lodging
Tall plants in rich soil or wind-exposed sites may flop after heavy rain. Stake with grow-through supports early in the season, or cut back by one-third in late spring (Chelsea chop) to produce sturdier, shorter stems.
Powdery mildew
Can appear in warm, humid late-summer conditions. Improve spacing between plants and avoid overhead watering. Remove badly infected stems to base; regrowth is usually clean.
Slugs on young shoots
Emerging spring growth is attractive to slugs and snails. Apply iron phosphate pellets or use beer traps around the crown when growth first appears in spring.
Prevent nettleleaf giant hyssop problems before they start
Most nettleleaf giant hyssop issues are care-mismatch, not bad luck. Dial in the basics:
Nettleleaf Giant Hyssop problems — FAQ
Why is my nettleleaf giant hyssop flopping or lodging?
Tall plants in rich soil or wind-exposed sites may flop after heavy rain. Stake with grow-through supports early in the season, or cut back by one-third in late spring (Chelsea chop) to produce sturdier, shorter stems.
Why is my nettleleaf giant hyssop powdery mildew?
Can appear in warm, humid late-summer conditions. Improve spacing between plants and avoid overhead watering. Remove badly infected stems to base; regrowth is usually clean.
Why is my nettleleaf giant hyssop slugs on young shoots?
Emerging spring growth is attractive to slugs and snails. Apply iron phosphate pellets or use beer traps around the crown when growth first appears in spring.