Repotting guide

When & how to repot Arisaema jacquemontii (Arisaema jacquemontii)

Also called Jacquemont's cobra lily, high-altitude arisaema.

More about arisaema jacquemontii

About Arisaema jacquemontii

Arisaema jacquemontii · also called Jacquemont's cobra lily, high-altitude arisaema · flowering

Arisaema jacquemontii is a hardy Himalayan cobra lily growing from a tuber, with a single divided leaf and an elegant green-and-white striped hooded spathe in late spring. Unlike its tropical relatives it tolerates cold, thriving in cool, humus-rich, well-drained woodland soil in part shade. A choice, deciduous tuberous perennial for shaded borders and woodland gardens in temperate climates.

Mature size: Reaches roughly 30-60 cm tall in flower, occasionally to 1 m in rich soil, forming a slowly increasing clump from offset tubers.

How to tell arisaema jacquemontii needs repotting

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

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, arisaema jacquemontii is lifted and divided once the clump congests and flowering drops off. Tuberous, deciduous perennial producing a single palmately divided leaf and a hooded green-and-white striped spathe in spring, dying back to a dormant tuber by late summer..

What size pot to step arisaema jacquemontii up to

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

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 jacquemontii in full growth or flower sets it back badly.

Step-by-step: repotting arisaema jacquemontii

Wait for dormancy. Let arisaema jacquemontii 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 cool, humus-rich, 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 jacquemontii, 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 jacquemontii

Arisaema jacquemontii wants cool, humus-rich, free-draining woodland soil. A leafy, moisture-retentive but sharply drained loam suits it best. Add leaf mould and grit; the tuber rots in heavy, wet winter ground, so improve drainage on clay soils. 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 jacquemontii — frequently asked questions

How often should you repot arisaema jacquemontii?

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

What size pot does arisaema jacquemontii need?

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

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

You lift and divide it. Arisaema jacquemontii 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 jacquemontii after repotting?

Hold off feeding arisaema jacquemontii 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.