Boston Fern
Nephrolepis exaltata · also called sword fern, Boston sword fern
The Boston fern is a lush, pet-safe classic with arching feathery fronds. It needs steady moisture, high humidity, and bright indirect light to look its best.
Nephrolepis exaltata is a graceful fern with arching, feathery fronds densely lined with small leaflets, prized as a classic hanging plant on porches and in bright bathrooms. Native to humid tropical and subtropical forests, it brings soft, full greenery and an old-fashioned, cottage-style charm to indoor spaces.
Boston ferns are non-toxic and pet-safe, but they are thirstier and more humidity-hungry than many houseplants, which makes them a bit more demanding indoors. Their delicate fronds drop leaflets and crisp up quickly in dry air or dry soil, so they reward attentive watering and humidity. Given the moisture they crave, they grow into impressively lush, fountain-like specimens.
How to care for Boston Fern
Light
Boston ferns prefer bright, indirect light, such as near an east window or a few feet from a brighter one. They tolerate some shade but grow thin and sparse in low light. Keep them out of direct sun, which scorches and dries the delicate fronds.
Watering
Keep the soil consistently and evenly moist, never letting it dry out fully, which often means watering every 3 to 5 days. Boston ferns are thirsty and quickly drop leaflets if they go dry. Water when the surface just begins to dry, and never let the plant sit in standing water.
Humidity
High humidity, ideally 50 percent or more, is essential for Boston ferns, which is why they thrive in bathrooms. Dry air causes crispy, browning fronds and leaflet drop. Use a humidifier, a pebble tray, or frequent misting to keep the air moist.
Temperature
Keep it between 60 and 75F. The fern prefers moderate, stable temperatures and dislikes heat above 80F and cold below 50F. Avoid drafts and the dry heat of nearby vents.
Soil & potting mix
Use a rich, well-draining but moisture-retentive potting mix, such as a peat-based blend with perlite. The soil should hold moisture without becoming waterlogged. A pot with drainage holes prevents root rot.
Feeding
Feed every 4 to 6 weeks during spring and summer with a balanced liquid fertilizer diluted to half strength. Ferns have modest nutrient needs and can suffer salt burn if over-fed. Stop feeding in fall and winter.
Pruning & grooming
Trim away brown or dead fronds at the base to keep the plant tidy and encourage fresh growth. Boston ferns naturally shed older fronds, so regular grooming is normal. Thin out crowded growth as needed.
Repotting
Repot every 1 to 2 years in spring when roots fill the pot, moving up one pot size. Large, congested clumps can be divided. Refresh the moisture-retentive mix to support lush growth.
Propagation
Propagate by division: split a mature plant into sections, each with roots and fronds, and pot them separately. Boston ferns also spread by runners that root into new plantlets. Spore propagation is possible but slow and rarely done at home.
Common Boston Fern problems
- Crispy, browning fronds. Brown, crispy fronds and dropping leaflets are the classic sign of air or soil that is too dry. Keep the soil evenly moist and raise humidity above 50 percent with a humidifier or pebble tray, especially in winter.
- Yellowing fronds. Yellowing can come from inconsistent watering, too little light, or low humidity. Keep moisture steady, move the fern to bright indirect light, and raise humidity around it.
- Massive leaflet drop. Showers of dropped leaflets usually follow a stressful change such as letting the soil dry out, low humidity, or a move to a hot, dry spot. Restore steady moisture, humidity, and stable conditions to recover.
Boston Fern FAQ
Why is my Boston fern turning brown and crispy?
Crispy, browning fronds almost always mean the air or the soil is too dry. Boston ferns need consistently moist soil and high humidity, so let the soil dry only at the very surface before watering again and aim for humidity above 50 percent. A humidifier, pebble tray, or a spot in a bright bathroom usually solves the problem.
Are Boston ferns safe for cats and dogs?
Yes, Boston ferns are non-toxic and safe for both cats and dogs, making them one of the better pet-friendly houseplants. Pets may still nibble the soft fronds, which can cause mild stomach upset from the fiber, but there is no poisoning risk. Hanging the fern also keeps it out of reach and protects the fronds.
How often should I water a Boston fern?
Boston ferns are thirsty and like their soil consistently moist, so you will often water every 3 to 5 days, watering whenever the surface just begins to dry. They should never dry out completely, as that causes rapid leaflet drop, but they also should not sit in standing water. Pair regular watering with high humidity for the lushest growth.