Repotting guide

When & how to repot Tufted Hair Grass (Deschampsia cespitosa)

Also called tufted hair grass, hassock grass.

More about tufted hair grass

About Tufted Hair Grass

Deschampsia cespitosa · also called tufted hair grass, hassock grass · flowering

Tufted hair grass is a cool-season, clump-forming perennial grass prized for airy, golden flower clouds that hover above dense evergreen mounds of fine arching foliage. Unusually shade-tolerant for an ornamental grass, it thrives in moist, cool, woodland-edge conditions and naturalises in damp meadows. Hardy and low-maintenance, it offers months of soft, translucent inflorescences from early summer.

Mature size: Foliage mound 30-60 cm tall; flowering stems reach 90-120 cm (about 3-4 ft) tall and 60-90 cm wide.

Watch for — Heat decline: As a cool-season grass it can look tired or go semi-dormant in hot, humid summers; site in cooler part shade and keep roots moist.

How to tell tufted hair grass needs repotting

Repotting on a calendar is less reliable than reading the plant. For tufted hair grass, watch for these signs:

Roots spiralling thickly out of the drainage holes or pushing the whole plant up out of the pot.
The pot is so packed that water runs straight through in seconds and barely wets the soil.
It has split a plastic pot, or the rootball is a solid mass with almost no soil left when you slide it out.
Growth and (for tufted hair grass) flowering have clearly stalled despite good light and feeding — but remember this plant likes being snug, so a little crowding alone is not a reason to repot.

For the underlying biology of a pot-bound root system and why it stalls a plant, see our guide to spotting and fixing a root-bound plant.

How often to repot tufted hair grass

Only every 2–4 years, when genuinely crowded. Tufted Hair Grass is one of the plants that genuinely prefers a snug pot — it grows and flowers better with its roots a little restricted, so resist the urge to repot it on schedule. Dense, semi-evergreen tufted clump of fine basal foliage sending up tall, gauzy flower panicles that rise well above the leaves and shimmer in the breeze..

What size pot to step tufted hair grass up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Tufted Hair Grass positively prefers a snug pot: it flowers and grows better when the roots are a little restricted. The single biggest repotting mistake here is over-potting — dropping tufted hair grass into a pot two or three sizes up. All that surplus soil holds water the small root system cannot use, stays cold and wet, and rots the roots within weeks. When in doubt, choose the smaller pot.

Not sure of the exact diameter? Our pot size calculator takes the current pot and root spread and tells you the right next size — it deliberately recommends a single step up, never a big jump.

The best time of year to repot tufted hair grass

Early spring, just as new growth restarts, is the ideal window for tufted hair grass. The plant is moving into its strongest growth phase and re-roots into fresh soil quickly. Avoid repotting in winter dormancy or, for flowering plants, while it is in bud or bloom — recovery is slowest then and you risk dropping the flowers.

Step-by-step: repotting tufted hair grass

Confirm it actually needs it. Slide tufted hair grass out and check the roots. Only continue if it is genuinely packed — this plant prefers a snug pot, so if there is still soil and room, put it straight back.
Pick a pot only one size up. Choose a pot just 2–3 cm wider with good drainage. Resist anything bigger; over-potting is the main killer here.
Ease it out gently. Water lightly the day before, then tip tufted hair grass out, supporting the base. Tease the outer roots free only enough to stop them circling.
Repot at the same depth. Add a layer of fresh moisture-retentive, humus-rich loam, set the plant so the soil line sits exactly where it did before, and backfill around the sides, firming lightly.
Settle it in. Water once to settle the soil, then let it sit. Hold off on more water until the top of the soil dries — fresh soil around a small root system stays wet for a while.

Aftercare

Because the new soil holds more water than the old crammed rootball did, ease right back on watering — let the top of the soil dry before you water tufted hair grass again, or you will rot the roots in the very pot you just moved it to. Keep it out of harsh direct sun for a fortnight. Do not fertilise for about 4 weeks — fresh mix already carries nutrients and feeding freshly disturbed roots scorches them.

The right soil mix for tufted hair grass

Tufted Hair Grass wants moisture-retentive, humus-rich loam. Best in fertile, evenly moist to damp soils, including heavy clay; tolerates a wide pH from acid to neutral. Avoid sharply drained, sandy or droughty sites where it sulks and browns out. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting tufted hair grass — frequently asked questions

How often should you repot tufted hair grass?

Only every 2–4 years, when genuinely crowded for tufted hair grass. Only repot tufted hair grass every 2–4 years, and only when it is genuinely root-bound — it flowers and grows best slightly crowded. Step up just one pot size in spring using moisture-retentive, humus-rich loam. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does tufted hair grass need?

When is the best time of year to repot tufted hair grass?

Does tufted hair grass like to be root-bound?

Yes — tufted hair grass genuinely flowers and grows best when slightly pot-bound, so do not rush to repot it. The mistake to avoid is over-potting into a much larger pot: the excess soil stays wet, the roots cannot use it, and the plant rots. Only repot every few years and only one snug size up.

Should you fertilise tufted hair grass after repotting?

Not immediately. Wait about 4 weeks after repotting tufted hair grass. Fresh mix already contains nutrients, and feeding freshly cut or disturbed roots burns them. Resume your normal feeding routine once you see new growth.