Nephrolepis exaltata
Quick answer
Visible pests or suspicious leaf spots on your Boston fern should be addressed early. Use the signs below to identify the problem and choose the right treatment.
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How to tell
Fine webbing in the leaf joints, tiny moving dots, and a stippled, dusty look to the leaves. They thrive in the dry air many homes have.
The fix
Rinse the fronds in the shower, then raise the humidity, which mites dislike, and repeat every few days until they are gone. Skip neem and other oils: they can burn fern fronds. If mites keep coming back, use a product whose label says it is safe on ferns. Isolate it from other plants.
Not a match? Compare the signs below to find the one you have.
How to tell
White, cottony fluff tucked into leaf joints and along stems, sometimes with sticky residue.
The fix
Pick them off with a cotton swab dipped in soapy water (rubbing alcohol can burn fern fronds) and check weekly: they hide. Skip whole-plant soap and oil sprays, which ferns handle badly. If they keep coming back, use a product whose label says it is safe on ferns.
How to tell
On a fern, first rule out spore cases: brown dots in regular rows on the underside of fronds are normal and should not be scraped off or treated. Small, brown, limpet-like bumps stuck to stems and the undersides of leaves, often with sticky honeydew.
The fix
Scrape them off gently with a fingernail or soft toothbrush and keep checking. Skip neem and other oils: they can burn fern fronds. If they keep coming back, use a product whose label says it is safe on ferns.
How to tell
Small black flies run across the soil and fly up when you water. Their larvae live in soil that stays damp.
The fix
This plant must not dry out, so water from below to keep the surface drier, catch the adults on yellow sticky traps, and treat the soil with a Bti larvicide as its label directs.
How to tell
Brown or black spots, often with a yellow halo, usually after the leaves stayed wet or the soil was overwatered.
The fix
Remove affected leaves, improve airflow, and water the soil rather than the leaves. Keep the soil evenly moist as this plant needs: wet leaves, not moist soil, spread leaf spot.
How to tell
Dry, bleached, or brown patches only where strong direct sun hits the leaf, with no bugs or webbing. Boston fern wants bright, indirect light.
The fix
Move it back from the glass, out of the strongest sun.
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