What's eating my osmunda spectabilis?

American royal fern is a large bog/streamside garden fern. Slugs and snails shred its soft emerging croziers. Deer browse heavily in moist woodland gardens. Osmunda sawfly caterpillars can skeletonize fronds rapidly in summer. Its large, lush fronds in reliably moist sites create ideal conditions for slug and deer damage throughout the growing season.

Croziers eaten before unfurling; holes across mature frond surfaces in wet conditions Iron-phosphate pellets; hand pick at night; avoid heavy bark mulch in which slugs overwinter

Large fronds and crown browsed to stubs; repeated browsing weakens the plant over seasons Deer exclusion fencing around bog/streamside plantings; repellent spray reapplied after rain

Fronds rapidly skeletonized by caterpillar-like larvae feeding in groups Hand pick larval clusters; apply spinosad-based spray for heavy infestations; inspect fronds weekly in early summer