Repotting guide

When & how to repot Autumn Arum (Arum pictum)

Also called Painted Arum, Autumn Lords-and-Ladies, Balearic Arum.

More about autumn arum

About Autumn Arum

Arum pictum · also called Painted Arum, Autumn Lords-and-Ladies · tropical

Arum pictum is a distinctive tuberous aroid from the western Mediterranean islands — Corsica, Sardinia, and the Balearics — that flowers in autumn when most arums are dormant. Its glossy, arrow-shaped leaves are often attractively marbled. All parts are toxic; the dark purple-black spathe and subsequent red berries are especially appealing and dangerous.

Mature size: 20-35 cm tall in leaf; spathe to about 15 cm

Watch for — No autumn flowers: Tuber too small or insufficient summer heat ripening; plant in a sunnier spot and ensure summer temperatures reach 20°C+.

How to tell autumn arum needs repotting

Repotting on a calendar is less reliable than reading the plant. For autumn arum, watch for these signs:

Flowering has tailed off year on year and the clump has become congested and overcrowded.
Lots of leaf and few flowers — a classic sign that autumn arum bulbs or tubers need lifting and dividing.
Bulbs visibly bursting the pot or pushing each other to the surface.
It is the natural dormancy window (foliage yellowed and died back) — the only safe time to lift and split.

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 autumn arum

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, autumn arum is lifted and divided once the clump congests and flowering drops off. Autumn-dormant tuberous perennial.

What size pot to step autumn arum up to

Pot size matters less than depth and spacing here. When you replant autumn arum, set the bulbs or tubers at the correct depth (a rough guide: two to three times their own height of soil over the top) and space them so they are not touching. A wide, shallow pot suits a clump better than a tall narrow one.

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 autumn arum

The only safe window is dormancy: wait until the foliage has yellowed and died back naturally, lift and divide then, and replant before or at the start of the next growing season. Disturbing autumn arum in full growth or flower sets it back badly.

Step-by-step: repotting autumn arum

Wait for dormancy. Let autumn arum foliage yellow and die back completely. Lifting while it is in growth wastes the energy it is storing for next year.
Lift carefully. Loosen the soil well away from the bulbs/tubers with a fork and ease the whole clump out without spearing them.
Separate the offsets. Gently pull the clump apart into individual bulbs or tubers. Keep only firm, healthy, blemish-free ones.
Replant at the right depth. Reset them in fresh gritty, humus-rich, free-draining mix at the correct depth and spacing — not touching — so each has room to bulk up.
Water in and rest. Water once to settle them, then keep on the dry side until growth resumes. Do not feed until leaves are actively growing.

Aftercare

After replanting autumn arum, keep the soil barely moist — not wet — until shoots appear; bulbs and tubers rot in cold, saturated soil. Once leaves are growing strongly, resume normal watering. Hold off feeding until the plant is in active growth again.

The right soil mix for autumn arum

Autumn Arum wants gritty, humus-rich, free-draining mix. A blend of loam, leaf mould, and horticultural grit in roughly equal parts suits the Mediterranean conditions it prefers. Excellent drainage is critical during the dry summer dormancy period. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting autumn arum — frequently asked questions

How often should you repot autumn arum?

Lift and divide every 3–4 years once clumps congest for autumn arum. Autumn Arum is lifted and divided, not "repotted". Every 3–4 years, once the foliage has died back and it is dormant, lift the clump, separate the offsets, and replant at the correct depth in gritty, humus-rich, free-draining mix. Crowding, not pot size, is what reduces flowering over time.

What size pot does autumn arum need?

When is the best time of year to repot autumn arum?

Do you "repot" autumn arum, or lift and divide it?

You lift and divide it. Autumn Arum grows from bulbs or tubers, so instead of repotting you wait for dormancy, lift the congested clump, separate the healthy offsets, and replant them at the right depth and spacing. Doing this every 3–4 years restores flowering.

Should you fertilise autumn arum after repotting?

Hold off feeding autumn arum until it is in active growth again. Fresh soil already carries enough nutrients to get it re-established, and feeding disturbed roots too soon does more harm than good.