Boston Fern Black Fronds: Natural Spores vs. Disease Problems

Natural Black Spots: Spores

Small black spots in regular rows on leaf undersides are spores—reproductive structures. This indicates a healthy fern. Do nothing.

Natural Aging

Older lower fronds brown/black as new growth emerges. Trim discolored fronds to keep plant tidy.

Problematic Blackening

• Nematodes: Brown/black spots or strips. Add compost to encourage beneficial fungi. Remove infected plants if severe.
• Bacterial soft rot: Small, spreading, soft brown/black spots with odor. Destroy infected plants.
• Leaf tip burn: Browning, withering tips. Destroy infected plants.
• Rhizoctonia blight: Irregular brownish-black spots starting near crown, spreading rapidly. Spray with fungicide.