Repotting guide

When & how to repot Cylindric Arum (Arum cylindraceum)

Also called Cylindrical Lords-and-Ladies, Alpine Arum.

More about cylindric arum

About Cylindric Arum

Arum cylindraceum · also called Cylindrical Lords-and-Ladies, Alpine Arum · tropical

Arum cylindraceum is a tuberous perennial aroid native to central and southern Europe into the Caucasus, producing arrow-shaped leaves in spring and a pale spathe with a purple spadix. It dies back in summer after setting vivid red berries. All parts are toxic — the bright berries are especially dangerous to children and pets.

Mature size: 20-40 cm tall in leaf; dies back completely in summer

How to tell cylindric arum needs repotting

Repotting on a calendar is less reliable than reading the plant. For cylindric arum, 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 cylindric arum 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 cylindric arum

Lift and divide every 3–4 years once clumps congest. Rather than a true repot, cylindric arum is lifted and divided once the clump congests and flowering drops off. Deciduous tuberous perennial.

What size pot to step cylindric arum up to

Pot size matters less than depth and spacing here. When you replant cylindric arum, 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 cylindric arum

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 cylindric arum in full growth or flower sets it back badly.

Step-by-step: repotting cylindric arum

Wait for dormancy. Let cylindric arum 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, well-draining loam 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 cylindric arum, 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 cylindric arum

Cylindric Arum wants humus-rich, well-draining loam. A mix of loam, leaf mould, and sharp sand mimics woodland floor conditions. Good drainage prevents tuber rot during the dormant period. Neutral to slightly alkaline pH is preferred. Always use fresh mix when you repot — reusing old, broken-down soil reintroduces the compaction and poor drainage you are repotting to fix.

Repotting cylindric arum — frequently asked questions

How often should you repot cylindric arum?

Lift and divide every 3–4 years once clumps congest for cylindric arum. Cylindric Arum 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, well-draining loam. Crowding, not pot size, is what reduces flowering over time.

What size pot does cylindric arum need?

When is the best time of year to repot cylindric arum?

Do you "repot" cylindric arum, or lift and divide it?

You lift and divide it. Cylindric Arum 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 cylindric arum after repotting?

Hold off feeding cylindric arum 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.