Mature size & growth rate

How big does wavy hair grass (Deschampsia flexuosa) get?

Also called wavy hair grass, crinkled hair grass.

More about wavy hair grass

About wavy hair grass

Deschampsia flexuosa · also called wavy hair grass, crinkled hair grass · flowering

Wavy hair grass is a delicate, wiry cool-season perennial grass of acid heathlands, moorlands, and open woodlands in Europe and North America. Its slender, hair-fine leaves form low, dark-green tussocks from which airy, wavy-stemmed panicles of tiny, glistening spikelets rise in early summer. Ideal for acid soils, heath gardens, and naturalised moorland settings with striking translucent flower clouds.

Mature size: Foliage tufts 15-30 cm tall; flowering stems reach 40-70 cm tall and 30-45 cm wide.

Watch for — Alkaline soil failure: Yellowing, poor growth, and death result from neutral or alkaline soils; test pH before planting and correct to below 6.5 with sulphur chips or plant in ericaceous compost.

Indoor size vs how big it gets in the wild

wavy hair grass 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 foliage tufts 15-30 cm tall. In the ground with no restriction it is a completely different plant — flowering stems reach 40-70 cm tall and 30-45 cm wide. — which is why the pot, the light and the pruning matter so much for the size you actually end up with.

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

wavy hair grass 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: do not fertilise; this grass naturally grows in nutrient-poor conditions and feeding encourages rank, floppy growth and can kill it in rich soils. no amendments other than acid mulch (pine bark) are recommended.

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

How to keep wavy hair grass smaller

You are not stuck with the maximum size. For wavy hair grass specifically, these are the levers, in order of impact:

Divide the clump every year or two — splitting wavy hair grass 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 wavy hair grass 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 wavy hair grass bigger or faster

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

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger.
Good light plus regular feeding maximises offset and runner production.
Leave plantlets and offsets attached and feed through the growing season for the fastest spread.

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

When wavy hair grass outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for wavy hair grass:

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

wavy hair grass size — frequently asked questions

How big does wavy hair grass get?

wavy hair grass reaches foliage tufts 15-30 cm tall when grown indoors, and far larger where it grows unrestricted (flowering stems reach 40-70 cm tall and 30-45 cm wide.). 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 wavy hair grass slow or fast growing?

wavy hair grass is a moderate grower. Expect three to six years to reach mature indoor size, gaining a steady amount each growing season. wavy hair grass 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 wavy hair grass 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 wavy hair grass smaller?

Divide the clump every year or two — splitting wavy hair grass 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 wavy hair grass grow bigger or faster?

Give it a wider pot and let the clump fill it — width is exactly how this plant gets bigger. Good light plus regular feeding maximises offset and runner production. Leave plantlets and offsets attached and feed through the growing season for the fastest spread.