Repotting guide

When & how to repot Hollow-Rooted Fumewort (Corydalis cava)

Also called Hollow-rooted fumewort, Hollow fumewort, Bird-in-a-bush.

More about hollow-rooted fumewort

About Hollow-Rooted Fumewort

Corydalis cava · also called Hollow-rooted fumewort, Hollow fumewort · flowering

Corydalis cava is a spring-ephemeral tuberous perennial native across a broad swathe of central and southern Europe, from the Pyrenees to Ukraine, colonising shaded woodland floors, hedgebanks, and rocky slopes. In late winter and early spring it produces elegant racemes of white, pale lilac, or purple spurred flowers before the divided, glaucous foliage yellows and vanishes by early summer. Its common name refers to the distinctive hollow centre of the mature tuber, in contrast to the solid tuber of C. bulbosa. Plant it under deciduous trees in humus-rich soil and let it self-seed to naturalise. All parts are toxic to cats and dogs.

Mature size: Flower stems 15–30 cm tall; established colonies spread gradually via self-seeding over many seasons.

How to tell hollow-rooted fumewort needs repotting

Repotting on a calendar is less reliable than reading the plant. For hollow-rooted fumewort, 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 hollow-rooted fumewort 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 hollow-rooted fumewort

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, hollow-rooted fumewort is lifted and divided once the clump congests and flowering drops off. Spring-ephemeral, tuberous perennial; shoots emerge from the hollow tuber in February, flower stems reach peak in March–April, and all above-ground growth disappears by June..

What size pot to step hollow-rooted fumewort up to

Pot size matters less than depth and spacing here. When you replant hollow-rooted fumewort, 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 hollow-rooted fumewort

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 hollow-rooted fumewort in full growth or flower sets it back badly.

Step-by-step: repotting hollow-rooted fumewort

Wait for dormancy. Let hollow-rooted fumewort 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, humus-rich, well-drained 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 hollow-rooted fumewort, 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 hollow-rooted fumewort

Hollow-Rooted Fumewort wants deep, humus-rich, well-drained woodland soil. Work in significant quantities of leaf mould, composted beech or oak leaves, or fine bark chippings to create the soft, open-textured woodland floor this plant thrives in. A mildly acidic to neutral pH of 6.0–7.0 is preferred; shallow, stony soils prevent normal tuber development. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting hollow-rooted fumewort — frequently asked questions

How often should you repot hollow-rooted fumewort?

Lift and divide every 3–4 years once clumps congest for hollow-rooted fumewort. Hollow-Rooted Fumewort 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, humus-rich, well-drained woodland soil. Crowding, not pot size, is what reduces flowering over time.

What size pot does hollow-rooted fumewort need?

When is the best time of year to repot hollow-rooted fumewort?

Do you "repot" hollow-rooted fumewort, or lift and divide it?

You lift and divide it. Hollow-Rooted Fumewort 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 hollow-rooted fumewort after repotting?

Hold off feeding hollow-rooted fumewort 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.