Repotting guide

When & how to repot Frosty Fern (Selaginella kraussiana 'Frosty')

Also called Frosty fern, Frosty spikemoss, Krauss' spikemoss, African clubmoss, Spreading clubmoss.

More about frosty fern

About Frosty Fern

Selaginella kraussiana 'Frosty' · also called Frosty fern, Frosty spikemoss · houseplant

Frosty fern is a mat-forming spikemoss (not a true fern) prized for its lacy green fronds with frosted white tips. It demands constant moisture, high humidity and bright indirect light, making it a classic terrarium plant. The ASPCA lists it as non-toxic to cats, dogs and horses, so it is pet-safe.

Mature size: Around 2-4 in (5-10 cm) tall, spreading 12-18 in (30-45 cm) wide

Watch for — Brown, crispy fronds: The classic symptom of low humidity or a dried-out root ball. Raise humidity (terrarium, cloche, humidifier) and never let the soil fully dry out.

How to tell frosty fern needs repotting

Repotting on a calendar is less reliable than reading the plant. For frosty 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 frosty 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 frosty fern

Every 1–2 years, disturbing the roots as little as possible. Frosty Fern's growth habit — low, creeping, mat-forming evergreen with a fast growth rate; trailing rooting stems spread horizontally to form a dense carpet. new growth emerges bright white or cream (the "frosted" tips), maturing to green. — sets the pace. Frosty fern is a mat-forming spikemoss (not a true fern) prized for its lacy green fronds with frosted white tips. It demands constant moisture, high humidity and bright indirect light, making it a classic terrarium plant. The ASPCA lists it as non-toxic to cats, dogs and horses, so it is pet-safe.

What size pot to step frosty fern up to

Go up only one size and handle the rootball as little as possible. Frosty 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 frosty fern

Early spring, just as new growth restarts, is the ideal window for frosty 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 frosty fern

Keep disturbance to a minimum. Frosty 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 rich, humus-heavy, moisture-retentive mix that still drains ready.
Slide the rootball out whole. Water the day before, then ease frosty 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 frosty 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 frosty fern

Frosty Fern wants rich, humus-heavy, moisture-retentive mix that still drains. Use an acidic to neutral (pH 6.0-7.0), peat- or coir-based mix high in organic matter with perlite for drainage. The medium must hold moisture without staying waterlogged. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting frosty fern — frequently asked questions

How often should you repot frosty fern?

Every 1–2 years, disturbing the roots as little as possible for frosty fern. Repot frosty 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 rich, humus-heavy, moisture-retentive mix that still drains, keep it warm and humid afterwards, and never bare-root or hard-prune the roots.

What size pot does frosty fern need?

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

Why does frosty fern sulk after repotting?

Frosty 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 frosty fern after repotting?

Not immediately. Wait about 4 weeks after repotting frosty 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.