Mature size & growth rate

How big does Wall Rue (Asplenium ruta-muraria) get?

Also called Wall Rue, Wall Rue Spleenwort.

More about wall rue

About Wall Rue

Asplenium ruta-muraria · also called Wall Rue, Wall Rue Spleenwort · flowering

Wall rue (Asplenium ruta-muraria) is a tiny, tufted evergreen spleenwort that colonises mortared walls, limestone rocks and old masonry across Europe. Its small, leathery, ferny fronds are blue-green and parsley-like. A true lime-lover, it is exceptionally drought- and cold-tolerant, thriving in cracks where little else grows, but resents rich soil and disturbance.

Mature size: Fronds just 3-12 cm long; plants form compact tufts only a few centimetres across.

Watch for — Competition and smothering: Mosses and vigorous neighbours can crowd out this slow, tiny fern. Keep its crevice clear of encroaching growth.

Indoor size vs how big it gets in the wild

Wall Rue 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 fronds just 3-12 cm long. In the ground with no restriction it is a completely different plant — plants form compact tufts only a few centimetres across. — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

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

Wall Rue is a slow grower. Realistically, expect many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Its feeding profile backs this up: do not feed. wall rue is adapted to nutrient-poor masonry and crevices; fertiliser causes soft, untypical growth and can kill it. leave it lean.

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

How to keep wall rue smaller

Good news — wall rue barely needs managing. If you do want to keep it tidy:

You rarely need to do anything: wall rue is so slow that it can sit in the same small pot for years.
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 wall rue bigger or faster

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

It is already in good light; consistent warmth and a balanced feed in spring and summer are the only levers.
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 wall rue light requirements page covers exactly how bright a spot it needs to grow at its potential instead of stalling.

When wall rue outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for wall rue:

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

Wall Rue size — frequently asked questions

How big does wall rue get?

Wall Rue reaches fronds just 3-12 cm long when grown indoors, and far larger where it grows unrestricted (plants form compact tufts only a few centimetres across.). It grows mostly by adding leaves, offsets or a slightly wider rosette rather than gaining height — the footprint barely changes year to year.

Is wall rue slow or fast growing?

Wall Rue is a slow grower. Expect many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Wall Rue 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 wall rue take to reach full size?

Roughly many years — it gains very little each season, so it can hold the same shelf-sized footprint for 5-10+ years. Light, pot size and feeding move that timeline more than anything else.

How do I keep wall rue smaller?

You rarely need to do anything: wall rue is so slow that it can sit in the same small pot for years. 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 wall rue grow bigger or faster?

It is already in good light; consistent warmth and a balanced feed in spring and summer are the only levers. 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.