Repotting guide

When & how to repot Climbing Onion (Bowiea volubilis)

Also called Climbing Onion, Sea Onion, Zulu Potato.

More about climbing onion

About Climbing Onion

Bowiea volubilis · also called Climbing Onion, Sea Onion · houseplant

Climbing Onion is a fascinating South African geophyte with a large, green, above-ground bulb that sends up slender twining stems armed with thread-like leaves. It prefers bright indirect light, infrequent watering, and a dry rest period after the vine dies back. An unusual and easy-to-grow collectors' succulent bulb that tolerates neglect well.

Mature size: Bulb to 15 cm diameter; vines can scramble to 1–2 m given support

How to tell climbing onion needs repotting

Repotting on a calendar is less reliable than reading the plant. For climbing onion, 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 climbing onion 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 climbing onion

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, climbing onion is lifted and divided once the clump congests and flowering drops off. Geophytic bulb with a large, fleshy, green, onion-like bulb that sits at or above soil level; sends up annual twining, leafless (or near-leafless) scrambling vine stems that die back seasonally..

What size pot to step climbing onion up to

Pot size matters less than depth and spacing here. When you replant climbing onion, 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 climbing onion

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 climbing onion in full growth or flower sets it back badly.

Step-by-step: repotting climbing onion

Wait for dormancy. Let climbing onion 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 well-draining succulent or cactus 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 climbing onion, 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 climbing onion

Climbing Onion wants well-draining succulent or cactus mix. Use a cactus/succulent blend or amend regular potting mix with 30–40% perlite or coarse sand. The bulb should sit half above the soil surface and must never sit in waterlogged conditions. pH 6.0–7.0. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting climbing onion — frequently asked questions

How often should you repot climbing onion?

Lift and divide every 3–4 years once clumps congest for climbing onion. Climbing Onion 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 well-draining succulent or cactus mix. Crowding, not pot size, is what reduces flowering over time.

What size pot does climbing onion need?

When is the best time of year to repot climbing onion?

Do you "repot" climbing onion, or lift and divide it?

You lift and divide it. Climbing Onion 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 climbing onion after repotting?

Hold off feeding climbing onion 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.