Repotting guide

When & how to repot White Arrow Arum (Peltandra sagittifolia)

Also called White Arrow Arum, Spoonflower, White Arrow-arum.

More about white arrow arum

About White Arrow Arum

Peltandra sagittifolia · also called White Arrow Arum, Spoonflower · flowering

A native southeastern US wetland perennial prized for its snowy-white, scoop-shaped spathe and glossy arrow-shaped leaves. It thrives in boggy margins, shallow ponds, and rain gardens. Plant in consistently wet or waterlogged soil in full sun to partial shade; tolerates standing water. Minimal fertiliser needed in rich organic soils. Spreads slowly by offsets.

Mature size: 60–90 cm tall (24–36 in), spread 45–60 cm (18–24 in)

How to tell white arrow arum needs repotting

Repotting on a calendar is less reliable than reading the plant. For white arrow arum, 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 white arrow arum) 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 white arrow arum

Only every 2–4 years, when genuinely crowded. White Arrow Arum 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. Clump-forming aquatic perennial emerging from stout rhizomes; deciduous in cold winters.

What size pot to step white arrow arum up to

Go up only one pot size — roughly 2–3 cm (about an inch) wider in diameter, no more. White Arrow Arum 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 white arrow arum 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 white arrow arum

Early spring, just as new growth restarts, is the ideal window for white arrow arum. 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 white arrow arum

Confirm it actually needs it. Slide white arrow arum 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 white arrow arum 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 wet, humus-rich loam or clay; ph 5.5–7.0, 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 white arrow arum 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 white arrow arum

White Arrow Arum wants wet, humus-rich loam or clay; ph 5.5–7.0. Accepts sandy, loamy, or heavy clay soils provided they remain waterlogged. Rich organic matter improves vigour. Does not need free drainage — waterlogging is desirable, not harmful. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting white arrow arum — frequently asked questions

How often should you repot white arrow arum?

Only every 2–4 years, when genuinely crowded for white arrow arum. Only repot white arrow arum 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 wet, humus-rich loam or clay; ph 5.5–7.0. The key mistake is over-potting: a too-big pot stays wet and rots the roots.

What size pot does white arrow arum need?

When is the best time of year to repot white arrow arum?

Does white arrow arum like to be root-bound?

Yes — white arrow arum 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 white arrow arum after repotting?

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