Identity & taxonomy
- Scientific name
- Pellaea rotundifolia (G.Forst.) Hook.
- Family
- Pteridaceae
- Genus
- Pellaea
- Order
- Polypodiales
- IUCN status
- Least Concern (LC)
- Wikidata
- Q7161522
- Pteris rotundifolia G.Forst.
- Platyloma rotundifolia (G.Forst.) J.Sm.
- Button fernen
- Round-leaved fernen
- Tarawera (Māori)en
- New Zealand cliff brakeen
- Knappormbunkesv
- Knappebregneno
- Knapbregneda
- Nappisaniainenfi
- Knopffarnde
New Zealand (North and South Islands; endemic)
How to identify it
Growth habit. Compact clumping evergreen fern with arching to nearly horizontal fronds emerging from a short underground rhizome. New fronds unfurl in classic fern fiddleheads (koru in Māori) from the rhizome and elongate over weeks. The plant adds 2–4 new fronds per year indoors. Older fronds yellow and dry from the tip; trim them out at the rhizome to keep the clump tidy.
Leaves. Pinnate fronds with 30–60 pairs of round to oval pinnae, each 10–15 mm across, arranged along a wiry dark brown to near-black rachis. Pinnae are leathery, dark green above, paler beneath, and entirely glabrous (no hairs). The 'button' appearance — round, separate, evenly spaced leaflets — is the diagnostic feature and entirely unlike the lacy or sword-shaped fronds of most popular ferns. Spore-bearing pinnae develop a brown sori band along the underside margin in late summer on mature plants.
- Round to oval leathery pinnae (each 10–15 mm) along a wiry near-black rachis.
- Pinnae are entire (smooth-margined) and glabrous, not divided or hairy.
- Compact clumping habit from an underground rhizome; arching frond posture.
- Tolerates drier air than any other commonly cultivated fern.
- Fronds emerge as fiddleheads (koru) in characteristic fern fashion.
Commonly confused with
Bird's nest fern
Completely different morphology: undivided strap-shaped fronds in a rosette ('bird's nest'), no separate round pinnae. Demands much higher humidity than button fern. Both pet-safe.
Boston fern
Lacy classic 'fern' frond — long sword-shaped fronds with finely divided narrow pinnae. Demands very high humidity, the opposite of button fern. Sheds dry leaflets prolifically.
Maidenhair fern
Delicate fan-shaped pinnules on hair-thin black stems. Notoriously demanding on humidity; collapses if soil dries even briefly. Maidenhair shares the wiry black stem with button fern but the pinnae are fan-shaped and divided, not round and entire.
Purple cliff brake
North American sister species, more drought-tolerant outdoors with lance-shaped purple-tinted pinnae. Rarely sold as a houseplant, but can be confused on plant labels because it shares the genus.
Care
Light
Medium to bright indirect light; avoids direct sun.
An east window, a north-bright window, or a south or west window 1.5–2 m back with a sheer curtain. Button fern tolerates lower light than most ferns and is a good choice for a desk corner or the dimmer end of a bookshelf. Direct unfiltered noon sun bleaches the leathery pinnae.
Seasonal: Nordic latitudes above ~55°N: button fern handles the dim October–March stretch better than Boston, maidenhair, or birds-nest ferns. A north-facing room is workable through winter.
Water
Water when the top 2 cm dries — typically every 7–10 days.
Unlike most cultivated ferns, button fern actively dislikes constantly wet soil. Allow the upper third of the rootball to dry between waterings, then water thoroughly until runoff. The species grows wild on rocky banks and forest margins, not in waterlogged cloud forest — root rot from sustained sogginess is the leading cause of death indoors.
Seasonal: Reduce watering by roughly a third in winter when growth slows.
Soil
Free-draining slightly alkaline mix with limestone chips or oyster shell.
Two parts peat-free houseplant mix, one part perlite or pumice, plus a small handful of crushed limestone or oyster shell. Pellaea rotundifolia is one of the few ferns that prefers slightly alkaline conditions — most ferns demand acid soil. The wild plant grows on calcareous (lime-rich) rocky banks in New Zealand.
Humidity
40–50 %; tolerates 30 %.
The killer feature of button fern as a houseplant is its tolerance of normal indoor air. Humidities that kill maidenhair and Boston ferns (30–40 %) are perfectly fine for button fern. Excessive humidity above 70 % combined with stagnant air actually invites fungal problems.
Temperature
13–22 °C; tolerates brief 7 °C.
Button fern is a temperate New Zealand species, not tropical. It tolerates noticeably cooler rooms than most ferns and is happy in a 15 °C bedroom or hallway. Sustained heat above 25 °C combined with dry air causes leaf scorch.
Fertilizer
Half-strength balanced feed monthly in spring and summer.
Button fern is a light feeder. Half-strength balanced NPK monthly during the growing season is sufficient. Over-fertilising shows as crispy frond tips and brown pinnae margins. Skip feeding from late October through February.
Pruning
Trim spent yellow fronds at the rhizome.
Cut yellowed or browned fronds out at the base of the petiole, close to the rhizome, with sharp scissors. New fronds emerge from the rhizome through the year; trimming old material keeps the clump tidy and lets new fronds emerge cleanly.
Repotting
Every 2–3 years in spring; the plant is slow.
Move up by one pot size only. Button fern's rhizome is shallow — repot loosely without burying the rhizome below soil level, or rot becomes a risk. Many growers refresh the top 3 cm of soil annually instead of repotting fully.
Division of the rhizome
moderate~Immediate — divisions carry existing rootsAt repotting time, lift the clump and tease apart into 2–3 sections, each with several fronds and a healthy share of rhizome and roots. Pot each into a small pot of fresh mix. Water once well, keep slightly shaded for 2 weeks, and resume normal care once new fronds appear. The most reliable propagation route.
Spore propagation
difficult~12–18 months to a small plantCollect spores from brown sori on the underside of mature fronds; sprinkle on the surface of damp sterile peat-free mix in a covered container. Prothalli (the gametophyte stage) emerge within 6–10 weeks; sporophytes (small fern plants) emerge over the following year. Slow, demanding, and almost never worth the effort given how easy division is — included for completeness.
Common problems
Fronds browning and dropping pinnae
Symptom
Fronds yellow at the tips and pinnae fall off; older fronds collapse first.
Cause
Either soil too wet (root rot) or, less commonly, soil too dry combined with very dry air. Root rot is more common because button fern is often killed by 'fern routine' watering — kept too wet.
Fix
Check soil 5 cm down. If wet, let dry fully and reduce watering frequency. If bone-dry, water thoroughly and consider raising humidity to 40 %. Trim out fully browned fronds at the rhizome.
Fronds going crispy and translucent
Symptom
Pinnae go pale, dry, and crisp, often with a translucent appearance.
Cause
Direct sunlight or sustained low humidity below 25 %.
Fix
Move out of direct sun to bright indirect light. Raise humidity if below 30 %. Existing damaged fronds don't recover; trim out and wait for new growth.
No new fronds for many months
Symptom
The plant looks alive but has not produced any new koru/fiddleheads.
Cause
Light too low, recent overwatering silently rotting the rhizome, or the plant is in winter dormancy.
Fix
Move closer to a window (medium-bright indirect). Check the rhizome for rot if soil has been wet for weeks. Wait until April-May if the lull is winter dormancy in a Nordic apartment.
White cottony tufts at frond bases
Symptom
Cottony white waxy tufts where fronds meet the rhizome.
Cause
Mealybugs sheltering at the rhizome — a favourite Pellaea pest.
Fix
Dab each visible mealy with a cotton bud dipped in 70 % isopropyl alcohol. Repeat weekly for 4 weeks because eggs hatch in waves. Inspect new fronds as they emerge.
Sudden collapse after repotting
Symptom
Several fronds yellow and die within weeks of a repot.
Cause
Rhizome buried too deep or roots disturbed too aggressively.
Fix
Unpot, raise the rhizome so its top is at or just above the soil surface, and gently re-firm soil around the roots. Hold off fertiliser for 2 months. Recovery usually takes 3–6 months.
- Mealybugs in the rhizome and frond bases
- Scale on fronds and stems
- Fungus gnats in damp soil
- Root rot from waterlogged soil (Pythium)
- Botrytis grey mould in stagnant high-humidity conditions
Toxicity & safety
No reported toxicity. The species has no documented poisoning cases in humans.
Pellaea rotundifolia — Missouri Botanical Garden Plant FinderASPCA classifies button fern (under the common name 'Cliff Brake') as non-toxic to cats. No oral irritation, no systemic toxicity reported. Safe for cat households.
Cliff Brake (Pellaea rotundifolia) — ASPCA Toxic and Non-Toxic PlantsASPCA classifies button fern as non-toxic to dogs. Safe for dog households.
Cliff Brake (Pellaea rotundifolia) — ASPCA Toxic and Non-Toxic PlantsWhy button fern breaks the 'ferns need humidity' rule
Almost every popular indoor fern — Boston, maidenhair, birds-nest, rabbit's foot, asparagus — comes from genuine high-humidity habitats: tropical cloud forest, swamp margins, riverbanks, deep wet shade. They struggle in dry indoor air below 50 % humidity, and the standard advice for fern owners is to invest in a humidifier or pebble tray. Button fern is the exception that proves the rule. It grows wild not in cloud forest but on rocky banks, scree slopes, and the sun-warmed bases of limestone cliffs in New Zealand — habitats where humidity drops well below 50 % during dry summer afternoons and the soil drains rapidly between rains.
Botanically, this matches the morphology you can see on the plant: leathery, almost succulent pinnae rather than the thin papery fronds of cloud-forest ferns; a sturdy water-storing rhizome; a glabrous (hairless) cuticle that minimises water loss. These are xeric (dry-adapted) features unusual for the family.
The practical consequence for indoor growers is that button fern is the easiest fern to keep alive in a Nordic apartment in winter, when central heating drives indoor humidity down to 25–35 %. Other ferns sulk and shed in those conditions; button fern carries on. If you want a 'fern look' on a desk or bookshelf without committing to a humidifier, this is the species to choose.
Telling button fern apart from the other ferns in the index
Ferns are easy to mistake for each other from a casual glance — green, frondy, often clumping. But button fern is among the most distinctive in cultivation, and a 30-second look at the pinnae shape clears up confusion every time.
The five most-cultivated ferns in our index look quite different up close. Boston fern (Nephrolepis) has long sword-shaped fronds with hundreds of narrow finely divided pinnae — the classic 'lacy fern' silhouette. Birds-nest fern (Asplenium) has undivided, strap-shaped fronds in a rosette — no separate pinnae at all. Maidenhair (Adiantum) has fan-shaped pinnules on hair-thin black wires, delicate and tightly packed. Asparagus fern (technically not a true fern at all but the name persists) has feathery green needle-like 'leaves' on long arching stems. And button fern (Pellaea rotundifolia) has clearly separate, round-to-oval, leathery pinnae arranged in pairs along arching dark wiry stems — a 'string of buttons' silhouette unlike any of the others.
The wiry near-black rachis (frond stem) is shared with maidenhair fern and is the only feature that occasionally causes confusion at a quick glance. The pinnae shape resolves it: maidenhair has small fan-shaped pinnules with notched edges; button fern has separate round buttons with smooth entire margins.
Button fern is one of a small minority of cultivated ferns that prefers alkaline (limestone-rich) soil rather than the acid peat conditions ferns are usually grown in. The wild plant grows on calcareous rocky banks and the bases of limestone cliffs in New Zealand — its closest cultivation analogue is rock-garden alpine soil rather than a fern grotto. Adding a small handful of crushed oyster shell or dolomite to the potting mix is one of the most reliable ways to keep an indoor button fern healthy long-term.
Frequently asked · 5
Is button fern safe for cats and dogs?+
Yes. ASPCA lists button fern (Pellaea rotundifolia, under the common name 'Cliff Brake') as non-toxic to both cats and dogs. It is one of the safer ferns for pet households alongside Boston fern and birds-nest fern.
Why is my button fern dying despite the humidity I'm giving it?+
Button fern is the rare fern that does not want high humidity — it grows wild on rocky banks and forest margins in New Zealand, not in cloud forest. Sustained humidity above 70 %, combined with constantly wet soil, invites root rot and grey mould. Cut watering frequency, let the top 2 cm dry between waterings, and stop misting — most button ferns labelled 'unhappy' are actually being killed with kindness.
How do I tell button fern from maidenhair fern?+
Both have wiry near-black rachises, which is where the confusion comes from. The pinnae are the giveaway. Button fern has separate, round-to-oval, leathery pinnae 10–15 mm across with smooth entire margins — 'a string of buttons'. Maidenhair fern has small fan-shaped pinnules with notched edges, packed densely in lacy whorls. Maidenhair also wilts dramatically if the soil dries; button fern shrugs.
Why is my button fern dropping pinnae?+
Most often soil too wet — button fern is much more drought-tolerant than other ferns and rots if kept saturated. Less often, soil too dry combined with very low humidity below 25 %. Check the soil 5 cm down: wet means overwatered, bone-dry means underwatered. Trim fully browned fronds out at the rhizome and adjust watering accordingly.
Can button fern handle a dim room?+
Yes — better than most ferns. Medium indirect light (5,000 lux) is enough, which corresponds to a north-facing window or 1.5–2 m back from a south/west window. It is one of the few ferns that does not strictly need bright indirect light, making it a good choice for an unlit corner of a Nordic apartment in winter.
- Best Ferns for a Dim Bathroom: 6 Species That Actually Survive Low Light + Steam
- Humidity for Houseplants: What Actually Matters (and What Doesn't)
- Are Houseplants Toxic to Cats and Dogs? A Quick-Scan Safety Guide
- Low-Light Houseplants That Actually Survive in Dim Corners
- Pet-Safe Houseplants: A Non-Toxic Guide for Cats and Dogs