Mature size & growth rate

How big does Mother Fern (Asplenium viviparum) get?

Also called Mother Fern, Viviparous Spleenwort.

More about mother fern

About Mother Fern

Asplenium viviparum · also called Mother Fern, Viviparous Spleenwort · houseplant

Asplenium viviparum, the mother fern, is a charming Malagasy fern that produces tiny plantlets (bulbils) directly on its finely divided fronds — a form of vivipary that makes propagation effortless. Elegant, feathery fronds arch gracefully from the centre. It thrives in humid, shaded indoor spaces and is perfect for terrariums or shaded bathrooms.

Mature size: 30–50 cm tall and 40–60 cm wide

Indoor size vs how big it gets in the wild

Mother Fern 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 30–50 cm tall and 40–60 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.

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

Mother 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 monthly through spring and summer with a balanced, water-soluble fertiliser at half the recommended strength. the finely textured fronds are sensitive to salt build-up — flush the pot with pure water every 2–3 months to remove accumulated minerals.

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

How to keep mother fern smaller

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

Divide the clump every year or two — splitting mother fern 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 mother fern 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 mother fern bigger or faster

If you want it to fill the space sooner, push the conditions rather than hoping — for mother fern 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 mother fern light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When mother fern outgrows the room (or the pot)

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

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

Mother Fern size — frequently asked questions

How big does mother fern get?

Mother Fern reaches 30–50 cm tall and 40–60 cm wide 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 mother fern slow or fast growing?

Mother Fern is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Mother Fern 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 mother 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 mother fern smaller?

Divide the clump every year or two — splitting mother fern 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 mother fern 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.