Repotting guide

When & how to repot Bushgrass (Calamagrostis arundinacea)

Also called Bushgrass, Reed small-reed, Woodland small-reed.

More about bushgrass

About Bushgrass

Calamagrostis arundinacea · also called Bushgrass, Reed small-reed · flowering

Calamagrostis arundinacea is a widespread ornamental grass native to Europe and Asia, found in woodland margins, scrub, and semi-shaded habitats from western Europe east to Japan. It forms arching clumps of narrow green leaves and produces feathery, purplish-tinted flower panicles in late summer that fade to a warm tan and persist into winter, providing excellent structural interest. It is notably tolerant of dry shade, making it valuable in difficult garden spots under trees. Calamagrostis grasses are not considered toxic to cats or dogs.

Mature size: 60–120 cm tall in flower and 60–90 cm wide (24–48 in × 24–36 in).

How to tell bushgrass needs repotting

Repotting on a calendar is less reliable than reading the plant. For bushgrass, 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 bushgrass) 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 bushgrass

Only every 2–4 years, when genuinely crowded. Bushgrass 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. Loosely arching, clump-forming deciduous grass producing erect flowering culms above a mound of narrow foliage; non-invasive, spreading slowly by short rhizomes..

What size pot to step bushgrass up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. Bushgrass 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 bushgrass 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 bushgrass

Early spring, just as new growth restarts, is the ideal window for bushgrass. 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 bushgrass

Confirm it actually needs it. Slide bushgrass 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 bushgrass 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 well-drained to moderately moist loam or sandy loam; tolerates dry soils, 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 bushgrass 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 bushgrass

Bushgrass wants well-drained to moderately moist loam or sandy loam; tolerates dry soils. Adaptable to a wide range of soil types including dry, infertile soils under trees; good drainage is preferred as prolonged waterlogging is poorly tolerated. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting bushgrass — frequently asked questions

How often should you repot bushgrass?

Only every 2–4 years, when genuinely crowded for bushgrass. Only repot bushgrass 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 well-drained to moderately moist loam or sandy loam; tolerates dry soils. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does bushgrass need?

When is the best time of year to repot bushgrass?

Does bushgrass like to be root-bound?

Yes — bushgrass 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 bushgrass after repotting?

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