Troubleshooting
Rosinweed problems — and how to fix them
Rosinweed (Silphium integrifolium) 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 in wet soils
Extended winter waterlogging or poorly drained summer soils can cause crown rot. Improve drainage before planting; on heavy clay, raise the planting level slightly or add grit to the planting hole.
Septoria and Cercospora leaf spots
Fungal leaf spots appear as brown or tan lesions on foliage in wet summers. Remove affected leaves, avoid overhead watering, and ensure good plant spacing for airflow.
Borer larvae
Papaipema stem borers occasionally tunnel into stems causing wilt. Cut out and destroy affected stems; no pesticide is reliably effective once larvae are inside the stem.
Prevent rosinweed problems before they start
Most rosinweed issues are care-mismatch, not bad luck. Dial in the basics:
Rosinweed problems — FAQ
Why is my rosinweed crown rot in wet soils?
Extended winter waterlogging or poorly drained summer soils can cause crown rot. Improve drainage before planting; on heavy clay, raise the planting level slightly or add grit to the planting hole.
Why is my rosinweed septoria and cercospora leaf spots?
Fungal leaf spots appear as brown or tan lesions on foliage in wet summers. Remove affected leaves, avoid overhead watering, and ensure good plant spacing for airflow.
Why is my rosinweed borer larvae?
Papaipema stem borers occasionally tunnel into stems causing wilt. Cut out and destroy affected stems; no pesticide is reliably effective once larvae are inside the stem.