Boston fern
Sources last read 14 September 2026.
Difficult One of the harder ones, and one of the reasons the diagnosis tool exists.
Also called boss fern, Boston swordfern, Bostonfern, Fluffy Ruffles, ladder fern and Wild Boston Fern.
Toxicity is partly unassessed
What the sources say about its care
- Light
- Partial shadeRHS · read 11 September 2026
- Water
- Moist but well-drainedRHS · read 11 September 2026
- Humidity
No source read publishes a humidity figure for any plant on this site. What follows is general guidance for foliage plants.
ASHRAE recommends indoor relative humidity between 30% and 60% 30–60%Penn State Extension · read 11 September 2026- Temperature
How cold this tolerates, not what it prefers. No source read for this site publishes a preferred range for a plant indoors.
H1B — 10–15°C 10–15 °CRHS · read 11 September 2026- Soil
- Loam, Sand; pH Acid or NeutralRHS · read 11 September 2026
- Toxic to cats
- Listed as non-toxicASPCA · read 11 September 2026
- Toxic to dogs
- Listed as non-toxicASPCA · read 11 September 2026
- Harmful to people
- No harm statement is published for this plant; that absence is not evidence it is safe.RHS · read 11 September 2026
How it usually goes wrong
- A thin dry rim that crumbles between the fingers
The boston fern shows browning on many fronds at once, all at the margin, with no spots or soft patches anywhere.
Leaf margins are the end of the water supply, so they are the first tissue to run short when the air takes more than the roots can send. Penn State Extension cites 30% to 60% as the recommended indoor range, and a heated room in winter sits below it.
Telling it apart: Look at the pot rim and the soil surface. A white crust points at a build-up from tap water or feed rather than at the air. Penn State also reports misting and pebble trays do little to the humidity around a plant.
Penn State ExtensionBoston fern leggy, leaning growth: causes- Growth slows and what does arrive is thin
Nothing browns and nothing drops; the boston fern simply makes less, and what it makes is stretched and thin.
A plant stretches when the light is short of what it evolved for. Its source describes partial shade, and a room darker than that sets the plant reaching.
Telling it apart: Turn the pot and wait a fortnight. New growth that swings back toward the window is answering a light question.
RHSBoston fern leggy, leaning growth: causes- Yellowing that begins at the lowest fronds
Whole fronds yellow at once rather than browning at a margin, and the boston fern looks deflated despite soil that has not dried since it was watered.
Its source describes soil that is moist but well-drained. Roots held below that are short of air, and roots short of air stop moving water, so the plant wilts in a wet pot.
Telling it apart: Whether new growth is affected too. Root damage shows up everywhere at once; ordinary leaf loss shows only in the oldest leaves.
RHSBoston fern leaves turning yellow: causes
Not sure which it is? Ask the diagnosis questions for Boston fern.
Routine care
- Watering
- Water less in winter, since the plant is dormant then and excess water can cause root rot.NC State Extension · read 13 September 2026In the growing season, water moderately using soft water and feed monthly with a balanced liquid fertiliser at half strength. Give little water in winter.RHS · read 13 September 2026
- Feeding
- While growing, water moderately using soft water and give a balanced liquid fertiliser at half strength each month.RHS · read 13 September 2026
- Propagation
- Raise from spores sown when ripe at 21°C (70°F). Detach runners that have rooted during late winter or early spring.RHS · read 13 September 2026
- Pruning
- Remove dead fronds.RHS · read 13 September 2026
- Pests and diseases
- Can be troubled by Florida fern caterpillar and fern scale.NC State Extension · read 13 September 2026Scale insects can attack it. Disease is uncommon, but fronds that stay too wet can rot.RHS · read 13 September 2026
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Photographs
About the plant
Nephrolepis exaltata, known as the sword fern or Boston fern, is a species of fern in the family Nephrolepidaceae. It is native to the Americas. This evergreen plant can reach as high as 40–90 centimetres (16–35 in), and in extreme cases up to 1.5 metres. It is also known as the Boston sword fern, wild Boston fern, Boston blue bell fern, tuber ladder fern, or fishbone fern.
From Wikipedia, CC BY-SA 4.0 · read 13 September 2026
- Native range
- Trop. & Subtrop. AmericaWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Tropical & Subtropical AmericaNC State Extension · read 13 September 2026TropicsRHS · read 13 September 2026
- Climate
- subtropicalWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026
- Growth form
- epiphyteWorld Checklist of Vascular Plants, June 2026 release, CC BY.Kew WCVP · read 13 September 2026Epiphyte, Fern, Herbaceous Perennial; habit cascading, creeping, weepingNC State Extension · read 13 September 2026Bushy (evergreen)RHS · read 13 September 2026
- Size
- Height 24–36 in; width 24–36 inNC State Extension · read 13 September 2026Height 0.5-1 metres; spread 1-1.5 metres after 2–5 yearsRHS · read 13 September 2026
- Flowering
- No flowers.NC State Extension · read 13 September 2026
Common problems with Boston fern
Other Nephrolepis
Plants with similar care
Sources
- ASPCA · read 11 September 2026
- Kew WCVP · read 13 September 2026
- NC State Extension · read 13 September 2026
- Penn State Extension · read 11 September 2026
- RHS · read 13 September 2026
- Wikipedia · read 13 September 2026
What this does not cover
The figures above are what published sources say, not measurements of the plant in your room. They say nothing about your pot size, your water, the season, or how far from the glass the plant stands, and those decide more than any figure here does.
Humidity has no species figure because no source read for this site publishes one, and the only temperature published for this plant is a cold floor. The simulator fills those gaps with general figures for its kind of plant, marked as general and listed on how we read sources. Where a toxicity row says the plant was not assessed, that is the absence of a finding and not a finding of safety.
If something is already wrong, the diagnosis tool asks about the soil, the window and the watering, which is where the answer usually is.