Repotting guide

When & how to repot Arisaema flavum (Arisaema flavum)

Also called yellow cobra lily, Himalayan yellow arisaema.

More about arisaema flavum

About Arisaema flavum

Arisaema flavum · also called yellow cobra lily, Himalayan yellow arisaema · flowering

Arisaema flavum, the yellow cobra lily, is a tuberous Himalayan woodlander grown for its hooded yellow spathes in early summer. It thrives in cool, dappled shade and humus-rich, moisture-retentive but free-draining soil. The tuber goes fully dormant after leaf die-back, needing dry winter rest. Hardy and elegant, it suits shaded borders and woodland gardens.

Mature size: Typically 30-50 cm tall, occasionally to 75 cm in rich soil, with a spread of around 20-30 cm.

Watch for — Scorched foliage: Leaves brown at the margins in too much direct sun or dry wind. Move to dappled shade and keep the root zone consistently moist during growth.

How to tell arisaema flavum needs repotting

Repotting on a calendar is less reliable than reading the plant. For arisaema flavum, 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 arisaema flavum 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 arisaema flavum

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, arisaema flavum is lifted and divided once the clump congests and flowering drops off. Herbaceous tuberous perennial that emerges in late spring with a single divided leaf and a hooded yellow-green spathe, then dies back to the tuber by autumn..

What size pot to step arisaema flavum up to

Pot size matters less than depth and spacing here. When you replant arisaema flavum, 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 arisaema flavum

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 arisaema flavum in full growth or flower sets it back badly.

Step-by-step: repotting arisaema flavum

Wait for dormancy. Let arisaema flavum 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 humus-rich, moisture-retentive but free-draining woodland soil 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 arisaema flavum, 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 arisaema flavum

Arisaema flavum wants humus-rich, moisture-retentive but free-draining woodland soil. Blend loam with leaf mould or compost and grit for drainage. A slightly acidic to neutral pH suits it. Plant tubers roughly 15-20 cm deep; the depth helps insulate them and anchors the tall stems. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting arisaema flavum — frequently asked questions

How often should you repot arisaema flavum?

Lift and divide every 3–4 years once clumps congest for arisaema flavum. Arisaema flavum 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 humus-rich, moisture-retentive but free-draining woodland soil. Crowding, not pot size, is what reduces flowering over time.

What size pot does arisaema flavum need?

When is the best time of year to repot arisaema flavum?

Do you "repot" arisaema flavum, or lift and divide it?

You lift and divide it. Arisaema flavum 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 arisaema flavum after repotting?

Hold off feeding arisaema flavum 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.