Mature size & growth rate

How big does Button fern (Pellaea rotundifolia) get?

Also called New Zealand button fern, tarawera.

About Button fern

Pellaea rotundifolia · also called New Zealand button fern, tarawera · houseplant

Button fern is a small evergreen from New Zealand and Australia with round dark green leaflets on wiry stems. More drought-tolerant than most ferns and pet-safe. Good for terrariums and small pots.

Pellaea rotundifolia, native to New Zealand and Australia where, unusually for a fern, it grows in rocky, comparatively dry habitats rather than damp forest floor.

Compact evergreen reaching only about 25cm, with pinnate fronds of round, deep-green leathery leaflets on dark brown, pink-scaled rachises that give it its name.

Mature size: 20-30 cm tall and wide

Watch for — Slow growth: Normal; button ferns are not rapid growers.

Sources: rhs.org.uk, gardenia.net

Indoor size vs how big it gets in the wild

Button fern is a naturally small plant — it stays shelf- and desk-sized for its whole life, so it never becomes a space problem. Indoors and in a pot, expect 20-30 cm tall and wide. A pot, your light levels and a little pruning are what set the final size in a home, far more than the plant's theoretical potential.

It grows mostly by adding leaves, offsets or a slightly wider rosette rather than gaining height — the footprint barely changes year to year.

Growth rate and years to mature

Button fern is a moderate grower. Realistically, expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Its feeding profile backs this up: quarter-strength balanced feed every 6-8 weeks in growing season.

Want this turned into the right next pot at the right moment? The pot size calculator and the button fern repotting guide cover when and how much to size up — pot size is one of the biggest levers on how fast button fern grows.

How to keep button fern smaller

Good news — button fern barely needs managing. If you do want to keep it tidy:

Divide or remove offsets when the pot looks crowded to keep button fern to a single tidy clump.
Keeping it slightly pot-bound and easing back on feed naturally caps the size.
Pinch or remove the oldest, tiredest leaves so energy goes into a compact, fresh-looking plant.

How to grow button fern bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for button fern the accelerators are:

Move it to brighter (but not scorching) light — that is the single biggest growth lever for a small plant.
A small step up in pot size every couple of years gives the roots a little more room without triggering a size jump.
Feed lightly through the growing season; this plant simply will not race however hard you push it.

Light is almost always the ceiling. The button fern light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When button fern outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for button fern:

Roots circling the bottom or pushing out of the drainage hole — it wants a pot one size up, not a bigger room.
Offsets crowding the surface so the original plant looks squashed.
Honestly, button fern rarely outgrows a room — outgrowing its pot is the only realistic limit.

If it is the pot rather than the room, it is a repotting job, not a goodbye — see the button fern repotting guide. If you want more of this plant instead of a bigger one, the button fern propagation guide turns prunings into new plants.

Button fern size — frequently asked questions

How big does button fern get?

Button fern reaches 20-30 cm tall and wide when grown indoors. It grows mostly by adding leaves, offsets or a slightly wider rosette rather than gaining height — the footprint barely changes year to year.

Is button fern slow or fast growing?

Button fern is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Button fern is a naturally small plant — it stays shelf- and desk-sized for its whole life, so it never becomes a space problem.

How long does button fern take to reach full size?

Roughly three to six years to reach mature indoor size, gaining a steady amount each growing season. Light, pot size and feeding move that timeline more than anything else.

How do I keep button fern smaller?

Divide or remove offsets when the pot looks crowded to keep button fern to a single tidy clump. Keeping it slightly pot-bound and easing back on feed naturally caps the size. Pinch or remove the oldest, tiredest leaves so energy goes into a compact, fresh-looking plant.

How can I make button fern grow bigger or faster?

Move it to brighter (but not scorching) light — that is the single biggest growth lever for a small plant. A small step up in pot size every couple of years gives the roots a little more room without triggering a size jump. Feed lightly through the growing season; this plant simply will not race however hard you push it.