Repotting guide

When & how to repot Anchomanes giganteus (Anchomanes giganteus)

Also called giant anchomanes, West African arum.

More about anchomanes giganteus

About Anchomanes giganteus

Anchomanes giganteus · also called giant anchomanes, West African arum · tropical

Anchomanes giganteus is a towering tropical African aroid, even more imposing than A. difformis, producing one immense, intricately divided leaf on a tall, spiny, marbled stalk from a massive underground rhizome. A seasonal grower from West and Central African forest, it dies back fully in the dry season. Its sheer scale makes it a dramatic specimen for large warm conservatories.

Mature size: Leaf and petiole frequently exceed 2 m tall, with a wide, deeply divided canopy.

Watch for — Rhizome rot: Watering during dormancy or poor drainage rots the large rhizome. Keep dry while resting and use a free-draining mix in a deep pot.

How to tell anchomanes giganteus needs repotting

Repotting on a calendar is less reliable than reading the plant. For anchomanes giganteus, 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 anchomanes giganteus 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 anchomanes giganteus

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, anchomanes giganteus is lifted and divided once the clump congests and flowering drops off. Very large tuberous/rhizomatous perennial producing a single giant, deeply dissected leaf on a tall spiny mottled petiole each season, dying back to a massive rhizome..

What size pot to step anchomanes giganteus up to

Pot size matters less than depth and spacing here. When you replant anchomanes giganteus, 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 anchomanes giganteus

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 anchomanes giganteus in full growth or flower sets it back badly.

Step-by-step: repotting anchomanes giganteus

Wait for dormancy. Let anchomanes giganteus 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 deep, rich, free-draining loamy 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 anchomanes giganteus, 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 anchomanes giganteus

Anchomanes giganteus wants deep, rich, free-draining loamy mix. Use a fertile, humus-rich soil amended with bark and grit for drainage, in a large, deep container to house the big rhizome and anchor the tall leaf. Good drainage prevents rhizome rot during rest. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting anchomanes giganteus — frequently asked questions

How often should you repot anchomanes giganteus?

Lift and divide every 3–4 years once clumps congest for anchomanes giganteus. Anchomanes giganteus 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 deep, rich, free-draining loamy mix. Crowding, not pot size, is what reduces flowering over time.

What size pot does anchomanes giganteus need?

When is the best time of year to repot anchomanes giganteus?

Do you "repot" anchomanes giganteus, or lift and divide it?

You lift and divide it. Anchomanes giganteus 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 anchomanes giganteus after repotting?

Hold off feeding anchomanes giganteus 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.