Identity & taxonomy
- Scientific name
- Nephrolepis exaltata (L.) Schott
- Family
- Nephrolepidaceae
- Genus
- Nephrolepis
- Order
- Polypodiales
- Wikidata
- Q158920
- Polypodium exaltatum L. (basionym)
- Aspidium exaltatum (L.) Sw.
- Boston fernen
- Sword fernen
- Tuber ladder fernen
- Wild Boston fernen
- Amböjssv
- Sverdbregneno
- Sværdbregneda
- Pihlajanlehtisaniainenfi
- Schwertfarnde
Florida · Mexico and Central America · Caribbean · South America · Tropical Africa · Polynesia
How to identify it
Growth habit. Rosette-forming epiphytic fern with a dense crown of arching pinnate fronds emerging from a short upright rhizome. Produces long wiry above-ground stolons ('runners') from the base that bear tiny tubers and eventually root to form new plants. Mature specimens fill a hanging basket with a cascading fountain of fronds.
Leaves. Fronds are long and pinnate, 30–120 cm in mature specimens, with 50–100 pairs of linear-to-lanceolate pinnae 3–8 cm long arranged regularly along the rachis. 'Bostoniensis' is bright to medium green; each pinna is slightly serrate along the margin. Texture is soft and papery, markedly more delicate than outdoor landscape ferns.
Flowers. Ferns do not flower. Reproductive sori (clusters of spore cases) form round, brown, raised dots in rows along the underside of fertile pinnae. Boston ferns rarely produce fertile spores in cultivation.
- Long, arching, pinnate fronds that gracefully droop when the plant is mature — the classic 'cascading fountain' silhouette.
- Pale wiry stolons ('runners') emerging from the base and trailing along or out of the pot.
- Round, raised, brown sori in double rows on the underside of mature pinnae (when fertile).
- Small tubers along the stolons — storage organs the plant uses during drought in the wild.
- Fronds shed individual leaflets ('pinnae') readily in dry air — a reliable signal of low humidity.
Commonly confused with
Sword fern / tuberous sword fern
Closely related species, but fronds stand more erect and are shorter (30–60 cm), and tubers on the rhizome are more numerous. Much more invasive outdoors than exaltata.
Asparagus fern
Not a true fern — an Asparagaceae. Feathery needle-like leaves on wiry stems; no pinnate fronds or sori. Thorns along the stem.
Cretan brake fern
True fern with distinct forked/dichotomous frond architecture — pinnae often forked or variegated with a white central stripe. Smaller and denser than Boston fern.
Care
Light
Medium to bright indirect light.
Place near a north window, or 1–2 m back from an east window with filtered light. Direct afternoon sun scorches the thin pinnae within an hour or two. In deep shade Boston fern survives but growth stalls and pinnae shedding accelerates. Avoid any direct summer sun through glass.
Seasonal: Nordic winters: a diffused full-spectrum LED helps maintain growth and reduces pinnae shedding from October through March.
Water
Keep evenly moist; water when the top 1 cm of soil feels dry.
Boston fern tolerates neither drought nor waterlogging. Water thoroughly until runoff, then empty the saucer. Let only the surface dry before watering again. In a well-lit summer room this can mean 2–3 times a week; in winter, weekly is usually enough. Sudden drying causes pinnae to shed en masse from the oldest fronds first.
Seasonal: Reduce frequency slightly in winter but never let the soil dry completely.
Soil
Light, airy, moisture-retentive peat-free mix.
A mix of 3 parts peat-free potting soil, 1 part perlite, and 1 part fine orchid bark works well. Pure potting compost holds too much water and compacts over time; pure bark mixes drain too fast. Leaf mould from a garden compost pile is a classic ingredient if available.
Humidity
50–80 %; the higher the better.
Boston fern is one of the most humidity-dependent common houseplants. Below 40 %, pinnae shed within days and fronds brown at the tips. A dedicated humidifier nearby is genuinely required in most homes — pebble trays alone are not enough. A bathroom with good natural light is one of the few spots in a typical home where Boston fern thrives without supplemental humidity equipment.
Temperature
15–24 °C.
Tolerates cooler rooms than many tropical houseplants — classic Victorian parlours were often 13–18 °C. Excessive heat above 27 °C, especially paired with dry air, accelerates pinnae shedding. Keep away from radiators and forced-air heating vents.
Fertilizer
Balanced liquid feed monthly in spring and summer, at half strength.
A balanced NPK (3-1-2 or 20-20-20) at half the label rate is ample. Ferns are light feeders; overdoing it burns the fine roots and produces crispy frond tips. Flush the soil with plain water every 2–3 months to leach salts.
Seasonal: Skip feeding from late October through February.
Pruning
Trim dead fronds at the base; cut back neglected plants aggressively in spring.
Remove entirely-browned fronds at the base with sharp scissors. For an overgrown or shedding plant, a spring renewal cut — all fronds trimmed to within 5 cm of the rhizome — triggers a flush of fresh growth from the crown within 4–6 weeks. Keep warm and moist during the recovery.
Repotting
Every 1–2 years, or when the rhizome pushes upward out of the pot.
Move up by one pot size in early spring. Boston fern grows fast and will circle its pot within a season in good conditions — the rhizome eventually breaks through plastic pots. Wide shallow pots suit the rhizome better than tall narrow ones.
Stolon rooting
easy~3–6 weeksBoston fern sends out pale wiry runners with tiny tubers at each node. Pin a stolon onto the surface of a small pot of moist potting mix (use a bent paperclip) while it is still attached to the mother plant; once the node establishes roots, cut the stolon to separate. The easiest and most reliable method.
Rhizome division
moderate~Immediate — divisions carry existing rootsUnpot a mature plant in spring, identify natural break points in the rhizome, and gently pull or slice the clump into 2–4 sections, each with a healthy crown and roots. Pot each division into fresh mix. Divisions typically pause visible growth for 2–4 weeks.
Spore sowing
difficult~3–6 months from spore to small plantPossible with fertile spore-bearing specimens, but technically demanding and slow. Fresh spores sown on sterile surface-watered peat in a covered dish germinate within a few weeks as a green film (prothallus), which eventually produces young ferns. Impractical when stolons and division are available.
Cultivars
'Bostoniensis'
The original cultivar and what most people mean by 'Boston fern'. A spontaneous sport of the species found in a Florida-to-Boston shipment in 1894, with longer, more arching, gracefully-drooping fronds than the wild species.
'Compacta'
Smaller, denser, more upright version of 'Bostoniensis' with shorter fronds — a better choice for small spaces where the classic Boston fern would sprawl.
'Fluffy Ruffles'
Densely ruffled cultivar with crested, overlapping pinnae that give each frond a fluffier appearance. Shorter than the type; more humidity-demanding.
'Dallas'
Compact cultivar bred for improved drought tolerance, marketed specifically for drier indoor environments. Shorter fronds and denser habit.
'Tiger Fern'
Variegated cultivar with irregular yellow-gold striping on the pinnae. Visually striking but slower-growing and more humidity-demanding than the plain form.
Common problems
Shedding pinnae ('fern blizzard')
Symptom
Individual leaflets fall off older fronds in quantity, carpeting the floor below the plant.
Cause
Dry air — humidity below 40 %. Winter heating combined with low humidity is the classic trigger. A secondary cause is drought stress from inconsistent watering.
Fix
Raise humidity above 55 % with a humidifier near the plant. Keep the soil evenly moist. If pinnae loss has stripped the plant bare, cut all fronds back to 5 cm above the rhizome in spring — fresh new growth emerges within 4–6 weeks in good conditions.
Brown, crispy frond tips
Symptom
Ends of fronds go brown and crispy.
Cause
Low humidity, under-watering, or accumulated salts from tap water or over-fertilising.
Fix
Raise humidity, water more consistently, and flush the soil with plain water every 2–3 months. Switch to filtered or rainwater if tap water is heavily chlorinated or fluoridated.
Yellowing entire fronds
Symptom
Whole fronds yellow from the base; new growth remains green.
Cause
Normal senescence on oldest fronds; overwatering if multiple fronds yellow at once; or inadequate light if new fronds are also pale and stunted.
Fix
A single yellow old frond at a time is expected. Multiple fronds together with wet soil means dial back watering; a generally pale plant needs more light.
Soggy, collapsing crown
Symptom
Central rhizome goes soft; whole fronds flop.
Cause
Rhizoctonia or Pythium rot from overwatering, cold soil, and poor drainage.
Fix
Unpot immediately. Trim mushy black rhizome sections and any affected roots with a clean knife. Repot any firm sections in fresh, airy mix and keep on the dry side until new growth appears. Recovery is possible if caught early.
- Spider mites
- Mealybugs
- Scale
- Fungus gnats
- Root rot (Pythium)
- Rhizoctonia crown rot
Toxicity & safety
No known toxic effect from handling or ingestion.
Nephrolepis exaltata — Missouri Botanical Garden Plant FinderASPCA lists Boston fern as non-toxic to cats. Ingestion of large amounts can cause mild GI upset from volume, not toxicity.
Boston Fern — ASPCA Toxic and Non-Toxic PlantsASPCA lists Boston fern as non-toxic to dogs.
Boston Fern — ASPCA Toxic and Non-Toxic Plants'Bostoniensis' — the cultivar that defined the species as a houseplant — was discovered in 1894 when a Philadelphia-based grower shipped a large consignment of Nephrolepis exaltata to Boston and noticed that one plant in the shipment had longer, more gracefully arching fronds than the others. That single sport was propagated by cuttings and spread through Victorian and Edwardian parlours within a decade. Virtually every 'Boston fern' sold today is a descendant of that one plant.
Frequently asked · 5
Is Boston fern safe for cats and dogs?+
Yes — ASPCA lists Boston fern as non-toxic to cats and dogs. It is one of the safer classic houseplants for pet households and is specifically recommended alongside spider plant and parlor palm as a cat-friendly option.
Why is my Boston fern shedding so many leaflets?+
Almost always dry air — humidity below about 40 % triggers a 'fern blizzard' of shed pinnae, especially in heated winter rooms. Raise humidity above 55 % with a humidifier nearby (pebble trays alone are usually not enough), keep the soil evenly moist, and consider moving the plant to a bathroom with natural light. If shedding has stripped the plant bare, a spring cut-back to 5 cm above the rhizome triggers fresh growth.
How often should I water a Boston fern?+
Keep the soil evenly moist. Water when the top 1 cm of soil feels dry — typically every 2–3 days in a bright summer room and every 5–7 days in winter. Never let the whole root ball dry out, and never leave the pot sitting in water.
Why are the fronds of my Boston fern turning brown at the tips?+
Low humidity, inconsistent watering, or salts and fluoride in tap water. Raise humidity above 55 %, water more regularly, and switch to filtered or rainwater. Flush the soil with plain water every 2–3 months to leach accumulated salts and reduce tip burn.
Can I propagate Boston fern at home?+
Yes — the easiest method uses the wiry runners (stolons) that emerge from the base of the plant. Pin a runner onto the surface of a small pot of moist potting mix using a bent paperclip while it's still attached to the mother; once the node establishes roots (3–6 weeks), cut the stolon to separate the new plant. You can also divide a mature clump at the rhizome in spring.