Mature size & growth rate

How big does Spike Moss (Selaginella kraussiana) get?

Also called Spike moss, Krauss' clubmoss, Krauss' spikemoss, African clubmoss, Japanese moss, Trailing Irish moss, Spreading club moss.

More about spike moss

About Spike Moss

Selaginella kraussiana · also called Spike moss, Krauss' clubmoss · houseplant

Spike moss (Selaginella kraussiana) is a low, creeping fern relative grown for its fine, feathery emerald foliage and mat-forming habit, ideal for terrariums. It demands constant moisture, very high humidity, and shade from direct sun. The ASPCA lists it as non-toxic to dogs, cats, and horses, making it pet-safe.

Mature size: Around 2-4 in (5-10 cm) tall, spreading 12-18 in (30-45 cm) or more; trim to control its rapid spread.

Indoor size vs how big it gets in the wild

Spike Moss 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) or more. In the ground with no restriction it is a completely different plant — trim to control its rapid spread. — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

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

Spike Moss is a fast grower. Realistically, expect one to three growing seasons — fast vines can add a metre or more of stem in a single good summer. Its feeding profile backs this up: feed lightly with a balanced liquid houseplant fertiliser diluted to half strength, roughly every 4-6 weeks from spring through autumn. avoid over-feeding, which causes brown leaf tips; do not fertilise in winter when growth slows.

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

How to keep spike moss smaller

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

Trim the longest vines back to the length you want — spike moss 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.
Expect to tidy it every few weeks in summer — this is a fast vine that will sprawl if left.

The keep-it-smaller method, step by step

Decide the length you want. Pick the point each vine of spike moss 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 spike moss bigger or faster

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

More (indirect) light dramatically lengthens the vines and enlarges the leaves.
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 spike moss light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When spike moss outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for spike moss:

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 spike moss repotting guide. If you want more of this plant instead of a bigger one, the spike moss propagation guide turns prunings into new plants.

Spike Moss size — frequently asked questions

How big does spike moss get?

Spike Moss reaches around 2-4 in (5-10 cm) tall, spreading 12-18 in (30-45 cm) or more when grown indoors, and far larger where it grows unrestricted (trim to control its rapid spread.). 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 spike moss slow or fast growing?

Spike Moss is a fast grower. Expect one to three growing seasons — fast vines can add a metre or more of stem in a single good summer. Spike Moss 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 spike moss take to reach full size?

Roughly one to three growing seasons — fast vines can add a metre or more of stem in a single good summer. Light, pot size and feeding move that timeline more than anything else.

How do I keep spike moss smaller?

Trim the longest vines back to the length you want — spike moss 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. Expect to tidy it every few weeks in summer — this is a fast vine that will sprawl if left.

How can I make spike moss grow bigger or faster?

More (indirect) light dramatically lengthens the vines and enlarges the leaves. 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.