Mature size & growth rate

How big does Erect Moss Fern (Selaginella erythropus) get?

Also called Red Selaginella, Ruby Spikemoss, Erect Spikemoss.

More about erect moss fern

About Erect Moss Fern

Selaginella erythropus · also called Red Selaginella, Ruby Spikemoss · houseplant

Selaginella erythropus is a striking spikemoss from tropical America with reddish-tinged undersides on its branching fronds. It forms neat, upright clumps ideal for terrariums and humid displays. Like most Selaginella, it carries no known toxicity and is not listed as harmful by the ASPCA.

Mature size: 15-25 cm tall, slowly spreading to 20-30 cm wide

Indoor size vs how big it gets in the wild

Erect Moss Fern is a naturally small plant — it stays shelf- and desk-sized for its whole life, so it never becomes a space problem. Indoors and in a pot, expect 15-25 cm tall, slowly spreading to 20-30 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.

It grows mostly by adding leaves, offsets or a slightly wider rosette rather than gaining height — the footprint barely changes year to year.

Growth rate and years to mature

Erect Moss 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 once a month during spring and summer with a balanced liquid fertiliser at quarter strength. stop feeding entirely in autumn and winter when growth slows.

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

How to keep erect moss fern smaller

Good news — erect moss fern barely needs managing. If you do want to keep it tidy:

Divide or remove offsets when the pot looks crowded to keep erect moss fern to a single tidy clump.
Keeping it slightly pot-bound and easing back on feed naturally caps the size.
Pinch or remove the oldest, tiredest leaves so energy goes into a compact, fresh-looking plant.

How to grow erect moss fern bigger or faster

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

Move it to brighter (but not scorching) light — that is the single biggest growth lever for a small plant.
A small step up in pot size every couple of years gives the roots a little more room without triggering a size jump.
Feed lightly through the growing season; this plant simply will not race however hard you push it.

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

When erect moss fern outgrows the room (or the pot)

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

Roots circling the bottom or pushing out of the drainage hole — it wants a pot one size up, not a bigger room.
Offsets crowding the surface so the original plant looks squashed.
Honestly, erect moss fern rarely outgrows a room — outgrowing its pot is the only realistic limit.

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

Erect Moss Fern size — frequently asked questions

How big does erect moss fern get?

Erect Moss Fern reaches 15-25 cm tall, slowly spreading to 20-30 cm wide when grown indoors. It grows mostly by adding leaves, offsets or a slightly wider rosette rather than gaining height — the footprint barely changes year to year.

Is erect moss fern slow or fast growing?

Erect Moss Fern is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Erect Moss Fern is a naturally small plant — it stays shelf- and desk-sized for its whole life, so it never becomes a space problem.

How long does erect moss 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 erect moss fern smaller?

Divide or remove offsets when the pot looks crowded to keep erect moss fern to a single tidy clump. Keeping it slightly pot-bound and easing back on feed naturally caps the size. Pinch or remove the oldest, tiredest leaves so energy goes into a compact, fresh-looking plant.

How can I make erect moss fern grow bigger or faster?

Move it to brighter (but not scorching) light — that is the single biggest growth lever for a small plant. A small step up in pot size every couple of years gives the roots a little more room without triggering a size jump. Feed lightly through the growing season; this plant simply will not race however hard you push it.