Mature size & growth rate

How big does Crown Fern (Blechnum discolor) get?

Also called Crown Fern, Piupiu, Petipeti.

More about crown fern

About Crown Fern

Blechnum discolor · also called Crown Fern, Piupiu · houseplant

Blechnum discolor is an elegant, evergreen New Zealand native fern found across both the North and South Islands, growing in damp, shaded forest understoreys. It produces a distinctive two-tier display: a crown of erect, narrow, dark-green fertile fronds surrounded by a skirt of arching, broader, paler-undersided sterile fronds, and mature plants develop a short trunk over time. Consistent moisture and shade are non-negotiable; it tolerates brief dry spells less well than other Blechnum species. Not listed as toxic to cats or dogs by the ASPCA.

Mature size: 50–120 cm tall and 50–100 cm wide at maturity (fronds can reach up to 1.2 m long).

Watch for — Slow establishment and transplant shock: Crown fern resents root disturbance and can drop fronds and stall after transplanting. Water in well with a diluted seaweed solution, avoid feeding for 6–8 weeks, and keep the rootball consistently moist until re-established.

Indoor size vs how big it gets in the wild

Crown Fern grows on a tree's timeline and scale — indoors it becomes a tall, trunked statement plant rather than a tabletop one. Indoors and in a pot, expect 50–120 cm tall and 50–100 cm wide at maturity (fronds can reach up to 1.2 m long).. 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 gains real height on a trunk or main stem, adding a tier of leaves a year and eventually reaching for the ceiling — this is a plant you grow up, not out.

Growth rate and years to mature

Crown 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 with a diluted balanced liquid fertiliser from spring to late summer; no feeding in autumn or winter.

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

How to keep crown fern smaller

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

The decisive tool is the secateurs: crown fern can be topped (cut the main growing tip) to cap its height and force a bushier, shorter shape.
Keeping it deliberately pot-bound in a snug container slows the whole plant and limits ultimate size.
Prune in spring so it heals fast; remove the tallest leader back to a node to reset the height.
Expect to top or hard-prune it every year or two — left alone it heads for the ceiling.

The keep-it-smaller method, step by step

Pick the new height. Decide how tall you want crown fern and find a leaf node or branch point just below that.
Top the main stem. Cut the main growing tip cleanly just above that node in spring; this permanently caps the height and forces side branches.
Keep the pot snug. Avoid jumping to a much bigger pot — a slightly restricted rootball keeps the whole plant smaller.
Maintain the shape. Prune back the tallest new leaders each spring to hold it at the height you chose.

How to grow crown fern bigger or faster

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

The biggest lever is light — a tree-type plant in dim light barely gains height; move it brighter.
Pot up a size every year or two while young; restricted roots are the main thing holding height back.
Feed regularly through the growing season and keep it warm — height comes from sustained good conditions.

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

When crown fern outgrows the room (or the pot)

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

The top leaves pressing against or bent by the ceiling — the classic "this is now too tall indoors" sign.
It has to be moved away from a light source it has literally outgrown.
Roots filling the largest pot you can reasonably keep indoors — at that point it is top-or-prune or move it outside (if hardy).

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

Crown Fern size — frequently asked questions

How big does crown fern get?

Crown Fern reaches 50–120 cm tall and 50–100 cm wide at maturity (fronds can reach up to 1.2 m long). when grown indoors. It gains real height on a trunk or main stem, adding a tier of leaves a year and eventually reaching for the ceiling — this is a plant you grow up, not out.

Is crown fern slow or fast growing?

Crown Fern is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. Crown Fern grows on a tree's timeline and scale — indoors it becomes a tall, trunked statement plant rather than a tabletop one.

How long does crown 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 crown fern smaller?

The decisive tool is the secateurs: crown fern can be topped (cut the main growing tip) to cap its height and force a bushier, shorter shape. Keeping it deliberately pot-bound in a snug container slows the whole plant and limits ultimate size. Prune in spring so it heals fast; remove the tallest leader back to a node to reset the height. Expect to top or hard-prune it every year or two — left alone it heads for the ceiling.

How can I make crown fern grow bigger or faster?

The biggest lever is light — a tree-type plant in dim light barely gains height; move it brighter. Pot up a size every year or two while young; restricted roots are the main thing holding height back. Feed regularly through the growing season and keep it warm — height comes from sustained good conditions.