Mature size & growth rate

How big does Moore's Blechnum (Blechnum moorei) get?

Also called Moore's Blechnum, Moore's Hard Fern.

More about moore's blechnum

About Moore's Blechnum

Blechnum moorei · also called Moore's Blechnum, Moore's Hard Fern · houseplant

Blechnum moorei is a compact, elegant hard fern native to Norfolk Island and New Caledonia, valued for its arching, ladder-like pinnate fronds with distinctly contrasting fertile and sterile leaves. It suits indoor cultivation in bright, humid rooms and is an excellent choice for terrariums or shaded windowsills where humidity is high.

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

Watch for — Yellowing fronds: Overwatering, poor drainage, or nutrient deficiency can cause yellowing. Check that the pot drains freely and reduce watering if soil stays wet. Apply a balanced feed if growth appears pale and stunted.

Indoor size vs how big it gets in the wild

Moore's Blechnum 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, 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

Moore's Blechnum 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: apply a half-strength balanced liquid fertiliser (e.g. 10-10-10 or similar) once a month from april to september. avoid feeding in autumn and winter when growth slows. over-fertilising causes frond tip burn from salt accumulation.

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

How to keep moore's blechnum smaller

You are not stuck with the maximum size. For moore's blechnum specifically, these are the levers, in order of impact:

Divide the clump every year or two — splitting moore's blechnum 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 moore's blechnum 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 moore's blechnum bigger or faster

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

When moore's blechnum outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for moore's blechnum:

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 moore's blechnum repotting guide. If you want more of this plant instead of a bigger one, the moore's blechnum propagation guide turns prunings into new plants.

Moore's Blechnum size — frequently asked questions

How big does moore's blechnum get?

Moore's Blechnum reaches 30–50 cm tall, 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 moore's blechnum slow or fast growing?

Moore's Blechnum is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Moore's Blechnum 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 moore's blechnum 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 moore's blechnum smaller?

Divide the clump every year or two — splitting moore's blechnum 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 moore's blechnum 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.