Mature size & growth rate

How big does Frosty Fern (Selaginella kraussiana 'Frosty') get?

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

Indoor size vs how big it gets in the wild

Frosty Fern does not get tall — it gets long. Size here is about stem length and how you train or cut it, not how much floor it claims. Indoors and in a pot, expect around 2-4 in (5-10 cm) tall, spreading 12-18 in (30-45 cm) 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.

Growth shows up as lengthening stems that trail down or climb up a support; the plant can be kept tiny or grown metres long from the exact same root system.

Growth rate and years to mature

Frosty 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: feed lightly about once a month during spring through autumn with a balanced liquid fertiliser diluted to half strength. skip feeding in winter. over-fertilising burns the delicate foliage and yellows the leaves, so err on the weak side.

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

How to keep frosty fern smaller

You are not stuck with the maximum size. For frosty fern specifically, these are the levers, in order of impact:

Trim the longest vines back to the length you want — frosty fern takes hard cutting well and bushes out from the cut.
Cut just above a leaf node; each trimmed stem usually branches into two, so pruning makes it fuller, not sparser.
The cuttings root easily in water or mix, so "keeping it smaller" doubles as free new plants.
A trim once or twice a season is usually enough to hold its length.

The keep-it-smaller method, step by step

Decide the length you want. Pick the point each vine of frosty fern should stop — you can be aggressive; it regrows readily.
Cut just above a node. Snip about 0.5 cm above a leaf node so the stem branches there instead of dying back.
Root the cuttings. Drop the trimmed pieces in water or mix — they root in 2-4 weeks and can fill the same pot for a bushier look.
Repeat as it runs. Re-trim whenever it overshoots; regular light pruning keeps it both smaller and fuller.

How to grow frosty fern bigger or faster

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

Good light plus a moss pole or trellis triggers the longest, fastest, largest-leaved growth.
Give it something to climb — many vines grow far faster and bigger up a support than trailing.
Feed through spring and summer and keep it consistently watered while it is actively running.

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

When frosty fern outgrows the room (or the pot)

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

Vines pooling on the floor or wrapping past where you want them — purely a trimming cue, not a repot one.
Bare, leggy stems with leaves only at the tips (usually a light problem, not a size one).
A tangled mass that has outrun its support and needs cutting back and re-training.

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

Frosty Fern size — frequently asked questions

How big does frosty fern get?

Frosty Fern reaches around 2-4 in (5-10 cm) tall, spreading 12-18 in (30-45 cm) wide when grown indoors. Growth shows up as lengthening stems that trail down or climb up a support; the plant can be kept tiny or grown metres long from the exact same root system.

Is frosty fern slow or fast growing?

Frosty Fern is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Frosty Fern does not get tall — it gets long. Size here is about stem length and how you train or cut it, not how much floor it claims.

How long does frosty 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 frosty fern smaller?

Trim the longest vines back to the length you want — frosty fern takes hard cutting well and bushes out from the cut. Cut just above a leaf node; each trimmed stem usually branches into two, so pruning makes it fuller, not sparser. The cuttings root easily in water or mix, so "keeping it smaller" doubles as free new plants. A trim once or twice a season is usually enough to hold its length.

How can I make frosty fern grow bigger or faster?

Good light plus a moss pole or trellis triggers the longest, fastest, largest-leaved growth. Give it something to climb — many vines grow far faster and bigger up a support than trailing. Feed through spring and summer and keep it consistently watered while it is actively running.