Guide
How to Care for a Boston Fern
The short answer
Boston ferns (Nephrolepis exaltata) want bright, indirect light, consistently moist soil, and high humidity. NC State Extension is blunt about the moisture rule: the soil should never be allowed to dry out. Keep the fern at 60–70°F and boost humidity by placing it near kitchens or bathrooms or setting the pot on a tray of wet pebbles.
Dry air is behind most Boston fern problems — it invites scale and spider mites and browns the fronds. In winter, when the plant is semi-dormant, reduce watering frequency, since overwatering then can lead to root rot. Boston ferns are listed as non-toxic to cats and dogs.
What a Boston Fern Is
Nephrolepis exaltata, the Boston or sword fern, is a classic hanging-basket foliage plant with arching fronds. Like all true ferns, it reproduces by spores rather than seeds — the dark brown to black dots on the undersides of fronds are normal spore cases, not a disease.
Light
Give bright, indirect light indoors. Outdoors the fern takes dappled sunlight to deep shade; direct hot sun scorches fronds.
Watering, Soil, and Drainage
Keep the soil consistently moist — never let it dry out completely. Use a loamy mix with good drainage so the roots stay moist but not waterlogged.
Humidity and Temperature
High humidity is essential. Place the fern near kitchens and bathrooms for naturally higher humidity, or set it on a tray of wet pebbles. Keep temperatures around 60–70°F.
Overwintering Indoors
Ferns summered outdoors should come inside before cold weather. During winter, growth slows: reduce watering frequency, because overwatering a semi-dormant fern can lead to root rot. Keep it in bright, indirect light away from hot, dry air vents.
Common Problems
- Brown, crispy fronds: air too dry — raise humidity with a pebble tray or a more humid room
- Scale or spider mites: both show up when the air around the plant is too dry
- Rows of dark dots under fronds: normal spores, not pests or disease
- Winter decline: usually overwatering during dormancy — water less often
→ NC State Extension lists Boston fern as non-toxic to cats, dogs, and horses — still, verify any plant against the ASPCA database if pets chew on houseplants.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- NC State Extension Gardener Plant Toolbox — Nephrolepis exaltata (Boston Fern) — Bright indirect light / shade tolerance, never let soil dry out, reduce winter watering to avoid root rot, pebble tray and kitchen/bathroom humidity advice, 60–70°F, scale and spider mites in dry air, spores normal, non-toxic to pets