Mature size & growth rate

How big does Porcupine Grass (Miscanthus sinensis 'Strictus') get?

Also called Porcupine grass, Banded miscanthus, Striped eulalia.

More about porcupine grass

About Porcupine Grass

Miscanthus sinensis 'Strictus' · also called Porcupine grass, Banded miscanthus · flowering

Miscanthus sinensis 'Strictus' is a bold, stiffly upright ornamental grass cultivar of the Chinese silver grass species, prized for its distinctive horizontal yellow-cream banding across the arching green leaf blades — a feature unique among upright miscanthus forms. In mid to late autumn it produces airy, pinkish-copper plume panicles that age to silvery-white and persist attractively through winter. The critical care point is full sun — without sufficient light, the characteristic yellow banding fades to plain green. It holds the RHS Award of Garden Merit. Miscanthus grasses are not listed as toxic by the ASPCA, but classified as mildly-toxic due to the potential for mechanical injury from sharp leaf edges and limited specific pet-safety data.

Mature size: 150–200 cm tall (to 250 cm with flower plumes), spreading 90–120 cm wide.

Watch for — Miscanthus mealybug: White waxy mealybugs shelter inside the stems, causing stunted or distorted growth that is difficult to eradicate once established. Monitor in spring when new growth emerges; treat with a systemic neonicotinoid-free insecticide, or remove and destroy heavily infested stems.

Indoor size vs how big it gets in the wild

Porcupine 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 150–200 cm tall (to 250 cm with flower plumes), spreading 90–120 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

Porcupine 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: apply a balanced slow-release granular fertiliser (e.g. 10-10-10) once in early spring as new shoots emerge; avoid high-nitrogen feeds that produce lax growth.

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

How to keep porcupine grass smaller

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

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

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

When porcupine grass outgrows the room (or the pot)

"Too big" usually arrives as one of these signs for porcupine 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 porcupine grass repotting guide. If you want more of this plant instead of a bigger one, the porcupine grass propagation guide turns prunings into new plants.

Porcupine Grass size — frequently asked questions

How big does porcupine grass get?

Porcupine Grass reaches 150–200 cm tall (to 250 cm with flower plumes), spreading 90–120 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 porcupine grass slow or fast growing?

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

Divide the clump every year or two — splitting porcupine 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 porcupine 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.