Boston fern (sword fern) care

Light

Boston fern prefers the middle of the household lighting range — bright enough to read by all day, but never in the direct path of midday sun. Medium to bright indirect light. Direct sun scorches the fronds; deep shade thins the plant out. A useful test: hold your hand a few centimetres above the leaves at noon. A faint hand shadow means good light; a sharp dark shadow means direct sun and likely too much for this species.

Watering

Water boston fern when the top 1 cm of soil is just dry, every 3-5 days. The actual day count varies with pot size, light level, and the season — the finger test (or, better, lifting the pot to feel its weight) is more reliable than a calendar. Empty any drainage saucer after watering so the pot is never sitting in water. Keep evenly moist with rainwater or filtered water — Boston ferns are sensitive to chlorine and minerals.

Soil and pot

Boston fern grows best in moisture-retentive houseplant compost. Peat-free compost with added coconut coir holds moisture without going soggy. A pot with a working drainage hole is non-negotiable for this species — even free-draining mix will turn soggy in a closed planter. If you love the look of a decorative pot without a hole, use it as a cachepot around an inner nursery pot you can lift out to water.

Humidity and temperature

Boston fern sits happiest at around 60-70% humidity and 15-24°C (60-75°F). High humidity is essential. Daily misting is not enough — use a humidifier. If you keep the room above 15 year-round and avoid placing the plant near a cold draught, a hot radiator, or an air-conditioning vent, you have already handled the two biggest indoor stressors.

Fertilising

Feed boston fern sparingly. Quarter-strength balanced feed every 4 weeks during the growing season; ferns are sensitive to over-feeding. Skip fertiliser entirely on a stressed, recently-repotted, or actively wilting plant — fertiliser salts make damage worse, not better. Wait for a round of healthy new growth before resuming a feeding rhythm.

Common problems

Below are the issues we see most often on boston fern in the Growli community. Each is annotated with the most common cause so you know where to start.

• Brown frond tips — Low humidity or tap-water minerals.
• Yellow fronds — Underwatering, sudden drying out, or too much direct sun.
• Massive frond shedding — Acclimation shock or a sudden change in humidity; trim back and improve conditions.
• Pale fronds — Insufficient light or under-feeding.

Companion plants

Boston fern pairs well with Calathea, Peace lily, and Spider plant. These are species with similar light and water needs, so you can group them in the same room or on the same shelf and water as a batch.

Propagation

Divide the rhizome at repotting; each division must have several healthy fronds and its own roots. Propagation is the cheapest, most satisfying way to expand a collection — and it doubles as insurance against losing a mature plant to an accident. Take a backup cutting once the parent is established and healthy.

Toxicity to pets

Boston fern is pet-safe. ASPCA lists Nephrolepis exaltata as non-toxic to cats and dogs. A safe lush option for pet households. If you keep cats, dogs, or curious children in the house, weigh placement carefully — a high shelf or a hanging planter is enough for casual safety. For severe ingestion incidents, call your local vet and the ASPCA Animal Poison Control Center (in the US, 888-426-4435).

Pet-safety status is sourced from the ASPCA Toxic and Non-Toxic Plant List, which catalogues the most-asked-about plants for cats, dogs, and horses.

Boston fern deep-dive guides

Every aspect of boston fern care, each with its own calibrated guide:

• Boston fern watering schedule
• Boston fern light requirements
• Best soil mix for boston fern
• Boston fern fertilizing guide
• When to repot boston fern
• How to propagate boston fern
• Boston fern growth rate & size
• Boston fern cold hardiness
• Boston fern temperature & humidity
• Is boston fern toxic to cats & dogs?

Related guides

Boston fern is also commonly called sword fern or Boston sword fern.

• Monstera care — light, water and common problems
• Pothos care — light, water and common problems
• Fiddle leaf fig care — light, water and common problems
• All 200 plant care guides in the Growli library