Soil & potting mix
Best soil for 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.
Preferred mix: Free-draining alkaline mix
Watch for — Brown crispy fronds: Dry soil; water more consistently.
Sources: rhs.org.uk, gardenia.net
Why button fern needs this mix
Button fern is a Mediterranean dry-hillside plant — it wants a lean, sharply drained, slightly alkaline mix, and rots fast in rich, water-holding soil.
- Button fern evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
- A lean, low-nutrient mix keeps growth firm and aromatic; a rich one gives soft, sappy, flavourless growth that flops and rots.
- It tolerates and often prefers a slightly alkaline soil, the opposite of most houseplants.
For the full picture on what makes up a good mix, see our guide to the main types of soil and potting media — it explains why each ingredient above behaves the way it does.
What goes wrong with the wrong mix
The wrong soil is one of the most common reasons button fern struggles, and the damage often shows up weeks later as a watering problem. For this species specifically:
- Rich, moisture-holding compost is the classic killer of button fern — especially over a cold, wet winter, when the base of the plant simply rots.
- A peaty, acidic potting mix is doubly wrong: too wet and the wrong pH direction.
- No grit means the rootball stays damp for days, which a dry-climate root system never copes with.
Growing button fern in ordinary rich, moisture-retentive compost. Lean it out with at least a third grit, and never let it sit wet over winter.
pH — does it matter for button fern?
Button fern likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
If you want to check or adjust it, the soil pH guide walks through testing and the safe ways to nudge a mix more acidic or more alkaline.
DIY mix vs a bagged one
Bagged "herb" or "Mediterranean" mixes are usually fine for button fern, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Drainage and the pot
Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
A gritty mix barely breaks down, so button fern needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. When the time comes, our repotting guide for button fern covers the timing and technique step by step.
Button fern soil — frequently asked questions
What is the best soil mix for button fern?
2 parts standard peat-free compost or loam : 1 part coarse horticultural grit : 1 part perlite or coarse sand. Button fern evolved on stony, sun-baked slopes — its roots expect to dry out hard and quickly between rains, so the mix must drain almost as fast as you pour.
Can I use normal potting soil for button fern?
Rich, moisture-holding compost is the classic killer of button fern — especially over a cold, wet winter, when the base of the plant simply rots. Bagged "herb" or "Mediterranean" mixes are usually fine for button fern, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
Does button fern need a special pH?
Button fern likes neutral to slightly alkaline soil, roughly pH 6.5-7.5. If your soil or compost is acidic, a little garden lime or extra grit nudges it the right way — the one common plant where you may add lime.
Should I buy a bagged mix or make my own for button fern?
Bagged "herb" or "Mediterranean" mixes are usually fine for button fern, but most standard composts need cutting hard with grit. The DIY ratio above is cheap and exactly right.
How often should I refresh the soil for button fern?
A gritty mix barely breaks down, so button fern needs little repotting — refresh the top layer and the grit every couple of years rather than potting on aggressively. Sharp drainage is everything: a terracotta pot with a big hole, gritty mix and never a saucer left full. Raised beds suit these herbs outdoors for the same reason.
Keep reading
- Button fern care — the full brief (light, water, humidity, problems, pet safety)
- How often to water button fern — the schedule the mix feeds into
- Repotting button fern — when and how to refresh the mix
- Soil pH guide — test it and adjust it safely
- Overwatered plant — signs and recovery
- Root rot — how the wrong soil starts it, and how to save the plant
- Should I water my plant? The simple check first
- Best soil for snake plant
- Best soil for dracaena
- Best soil for peperomia
- All 200 soil and potting-mix guides in the Growli library