Repotting guide

When & how to repot Button fern (Pellaea rotundifolia)

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.

A moderately fertile, ericaceous (lime-free), moist but well-drained mix; it forms a low, near-flat rosette ideal for terrariums and bottle gardens.

Mature size: 20-30 cm tall and wide

Sources: rhs.org.uk, gardenia.net

How to tell button fern needs repotting

Repotting on a calendar is less reliable than reading the plant. For button fern, watch for these signs:

Roots creeping out of the drainage holes or matting tightly across the soil surface.
The rootball dries out within a day or two no matter how much you water.
Water channels straight down the gap between rootball and pot without wetting the centre.
Steady decline — thin growth, persistent crispy edges — that good humidity and watering have not fixed. Only then is the disturbance of a repot worth the risk for button fern.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot button fern

Every 1–2 years, disturbing the roots as little as possible. Button fern's growth habit — compact clumping fern — sets the pace. 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.

What size pot to step button fern up to

Go up only one size and handle the rootball as little as possible. Button fern resents root disturbance, so the goal is to slide the intact rootball into slightly more soil — not to tease, wash or prune the roots. A modest step up means less shock and a faster recovery.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot button fern

Early spring, just as new growth restarts, is the ideal window for button fern. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting button fern

Keep disturbance to a minimum. Button fern resents root disturbance, so the plan is to move the intact rootball — not to wash, tease or prune the roots.
Choose just one size up. Pick a pot only one size larger with drainage, and have moisture-retentive free-draining alkaline mix ready.
Slide the rootball out whole. Water the day before, then ease button fern out keeping the rootball intact. Gently free only the roots that are circling the very bottom.
Nestle it into fresh soil. Add a base layer of fresh mix, set the rootball in at the same depth, and backfill gently around the sides without packing hard.
Water and protect. Water in, then keep it warm, humid and out of direct sun for a few weeks while it re-roots. Expect a short sulk — that is normal.

Aftercare

Expect button fern to sulk for a couple of weeks — that is normal after any root disturbance for this group. Keep it warm, humid and out of direct sun, water just enough to keep the mix lightly moist, and do not panic and overwater while it re-roots. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for button fern

Button fern wants free-draining alkaline mix. Compost with 25% perlite; tolerates slightly alkaline soil. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting button fern — frequently asked questions

How often should you repot button fern?

Every 1–2 years, disturbing the roots as little as possible for button fern. Repot button fern every 1–2 years, disturbing the roots as little as possible — it sulks for weeks if the rootball is teased apart. Slide it into one size up in spring with fresh free-draining alkaline mix, keep it warm and humid afterwards, and never bare-root or hard-prune the roots.

What size pot does button fern need?

When is the best time of year to repot button fern?

Why does button fern sulk after repotting?

Button fern resents root disturbance, so a wilt or stall for a week or two after repotting is normal, not a failure. Minimise it by keeping the rootball intact, stepping up just one size, and keeping the plant warm, humid and out of direct sun while it re-roots.

Should you fertilise button fern after repotting?

Not immediately. Wait about 4 weeks after repotting button fern. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.