Mature size & growth rate

How big does Spreading Spike Moss (Selaginella kraussiana) get?

Also called Krauss's Spike Moss, Mat Spikemoss, Trailing Spike Moss.

More about spreading spike moss

About Spreading Spike Moss

Selaginella kraussiana · also called Krauss's Spike Moss, Mat Spikemoss · houseplant

Spreading Spike Moss is a fast-growing, mat-forming spike moss native to the Azores, Canary Islands, and parts of Africa, widely naturalised in many warm-temperate regions. Its bright emerald-green, moss-like foliage spreads readily across moist soil. Ideal for terrariums and humid shelves. Not toxic to cats and dogs.

Mature size: 2-5 cm tall, spreading indefinitely across moist surfaces

Watch for — Legginess: Insufficient light leads to sparse, stretched growth. Move to a brighter indirect-light position.

Indoor size vs how big it gets in the wild

Spreading Spike Moss stays fairly low but widens over time — it spreads into a bigger clump by offsets, runners or rhizomes rather than shooting upward. Indoors and in a pot, expect 2-5 cm tall, spreading indefinitely across moist surfaces. 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.

Size here is about width, not height: the plant builds an ever-wider clump or sends out plantlets and runners while staying relatively short.

Growth rate and years to mature

Spreading Spike Moss is a fast grower. Realistically, expect two to four years from a young plant to a room-filling specimen in good light. Its feeding profile backs this up: feed with a very dilute balanced liquid fertiliser at quarter strength once a month during the growing season. over-fertilising will cause lush but weak, disease-prone growth.

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

How to keep spreading spike moss smaller

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

Divide the clump every year or two — splitting spreading spike moss is the main way to control its spread and refresh it.
Remove runners, plantlets or offsets as they appear if you want it to stay a single tight clump.
Keep it slightly pot-bound; a snug pot naturally limits how wide the clump can get.

The keep-it-smaller method, step by step

Lift the whole plant. Slide spreading spike moss out of its pot in spring when the clump has filled it.
Split the clump. Tease or cut the rootball into two or more sections, each with healthy roots and growth.
Repot one division. Put a single division back in the original pot to reset it to a smaller size; pot or give away the rest.
Remove offsets as they form. Through the year, detach new runners or pups to stop it spreading again.

How to grow spreading spike moss bigger or faster

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

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger.
Brighter light speeds up clump and offset production noticeably.
Leave plantlets and offsets attached and feed through the growing season for the fastest spread.

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

When spreading spike moss outgrows the room (or the pot)

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

The clump bulging over the pot rim or splitting the pot — the cue to divide, not to find a bigger room.
A dense centre that goes bare or tired while the edges keep spreading.
Runners or offsets escaping across the shelf or into neighbouring pots.

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

Spreading Spike Moss size — frequently asked questions

How big does spreading spike moss get?

Spreading Spike Moss reaches 2-5 cm tall, spreading indefinitely across moist surfaces when grown indoors. Size here is about width, not height: the plant builds an ever-wider clump or sends out plantlets and runners while staying relatively short.

Is spreading spike moss slow or fast growing?

Spreading Spike Moss is a fast grower. Expect two to four years from a young plant to a room-filling specimen in good light. Spreading Spike Moss stays fairly low but widens over time — it spreads into a bigger clump by offsets, runners or rhizomes rather than shooting upward.

How long does spreading spike moss take to reach full size?

Roughly two to four years from a young plant to a room-filling specimen in good light. Light, pot size and feeding move that timeline more than anything else.

How do I keep spreading spike moss smaller?

Divide the clump every year or two — splitting spreading spike moss is the main way to control its spread and refresh it. Remove runners, plantlets or offsets as they appear if you want it to stay a single tight clump. Keep it slightly pot-bound; a snug pot naturally limits how wide the clump can get.

How can I make spreading spike moss grow bigger or faster?

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger. Brighter light speeds up clump and offset production noticeably. Leave plantlets and offsets attached and feed through the growing season for the fastest spread.