Repotting guide

When & how to repot Ribbon Grass (Phalaris arundinacea 'Picta')

Also called ribbon grass, gardeners garters, variegated reed canary grass.

More about ribbon grass

About Ribbon Grass

Phalaris arundinacea 'Picta' · also called ribbon grass, gardeners garters · flowering

Ribbon grass, or gardener's garters, is a cool-season variegated grass with bright white-and-green striped blades, sometimes flushed pink in cool weather. Extremely vigorous and rhizomatous, it spreads aggressively and is considered invasive in many regions, so containment is essential. Tough and adaptable, it tolerates sun or shade, wet or dry soil, making it a resilient but assertive groundcover.

Mature size: Foliage typically 60-90 cm (2-3 ft) tall, with flower stems to about 120 cm; spread is potentially unlimited by rhizomes unless contained.

Watch for — Invasive spreading: Runs rampantly by rhizomes and is invasive in many areas, escaping into wetlands; plant only in containers or with strong root barriers.

How to tell ribbon grass needs repotting

Repotting on a calendar is less reliable than reading the plant. For ribbon 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 ribbon 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 ribbon grass

Only every 2–4 years, when genuinely crowded. Ribbon 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. Vigorous, rhizomatous, colony-forming grass with upright white-and-green variegated blades and airy flower panicles; an aggressive spreader rather than a clump..

What size pot to step ribbon grass up to

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

Early spring, just as new growth restarts, is the ideal window for ribbon 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 ribbon grass

Confirm it actually needs it. Slide ribbon 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 ribbon 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 adaptable, moisture-retentive soil, 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 ribbon 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 ribbon grass

Ribbon Grass wants adaptable, moisture-retentive soil. Grows in almost any soil from boggy to average garden loam and clay, across a wide pH. Moist, fertile ground gives the lushest growth but also fuels its aggressive spread. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting ribbon grass — frequently asked questions

How often should you repot ribbon grass?

Only every 2–4 years, when genuinely crowded for ribbon grass. Only repot ribbon 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 adaptable, moisture-retentive soil. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does ribbon grass need?

When is the best time of year to repot ribbon grass?

Does ribbon grass like to be root-bound?

Yes — ribbon 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 ribbon grass after repotting?

Not immediately. Wait about 4 weeks after repotting ribbon 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.