How to Propagate an Elephant Ear from Offsets, Runners and Division

Three routes, all of them easy

Colocasia is one of the simplest large plants to increase. It makes offsets, small corms that form against the parent underground; it produces runners, thin horizontal stems that travel outward and root a plantlet at the tip; and an established clump can simply be pulled apart into several crowns. All three work, and none of them needs any special equipment.

What it does not do reliably in cultivation is set viable seed. Flowering is uncommon indoors, the flowers are unremarkable, and seed is slow and unpredictable compared with lifting a corm you already have. Cuttings do not work either: there is no stem node to root from, only leaf stalks that will rot in water. Everything useful comes from the corm and what it produces.

Taking offsets at repotting

This is the method to use by default because it costs you nothing extra. When you tip the plant out to repot it in spring, look around the base of the main corm. You will usually find one to several firm little corms, anywhere from the size of a marble to the size of a hen's egg, each with a few roots and often a bud or a tiny leaf. Those are complete plants in waiting.

1. Wash enough compost off to see clearly Rinse the base of the rootball under a tap or in a bucket until you can see where each offset joins the parent. Working blind in wet compost is how you tear roots off pieces you meant to keep.
2. Separate by hand where you can Many offsets come away with a gentle twist and already have their own roots. Anything that separates cleanly by hand needs no cutting and no drying off, and can be potted straight away.
3. Cut the stubborn ones cleanly Where an offset is joined by a thick neck of tissue, cut it with a clean sharp blade rather than tearing it. Aim to leave a little of the parent tissue on the offset rather than a torn crater on either piece.
4. Dry any cut surfaces for a day Stand cut pieces in a dry airy place out of the sun for twenty-four hours so the wound seals. A fresh wet cut potted straight into damp compost is the main cause of losses.
5. Pot small and shallow Use a pot only slightly wider than the offset, with the top of the corm level with the surface. A small pot warms quickly and does not stay sodden around a piece that has few roots to drink with.
6. Keep warm, damp, not wet Hold it at 70 to 77F (21 to 25C) and keep the compost damp but do not stand it in water until it has two proper leaves of its own and is clearly growing.

Bare offsets have no leaf area, so they use very little water. This is the one stage of a colocasia's life where the ordinary warning applies: a leafless corm sitting in cold wet compost will rot rather than sprout.

Runners and plantlets

Through summer a vigorous plant sends out thin horizontal stems, often a foot (30 cm) or more long, which travel across or just under the compost and produce a small plant at the tip. In open ground these are how a colony spreads. In a pot they usually appear over the rim and hang down the side, and people mistake them for damaged stalks and cut them off.

Do not. Peg the tip into a small pot of compost standing beside the parent, using a bent wire or a stone to hold it in contact, and keep it damp. It roots within two to three weeks in warm weather. Once it is clearly anchored and growing on its own, cut the runner about an inch (3 cm) from the new plant and you have a free, well established plant with no check at all.

Dividing a clump, and cutting a large corm

After two or three seasons a plant kept from year to year becomes a clump of several crowns sharing one mass of corms and roots. Early spring, as growth restarts, is the time to break it up. Tip the whole thing out, wash the base so you can see the structure, and work the clump apart into pieces that each have at least one growing point and a share of roots. Pull and lever rather than sawing through the middle at random.

A single very large corm can also be cut into pieces, each with a visible bud, in the same way as a potato. This gives you more plants but carries real risk of rot, so treat every cut face with care: dust it with sulfur or leave it to dry hard for two days, pot into barely damp compost, and keep it warm and on the dry side until leaves appear.

Keeping track of what you made

Propagation is where records pay for themselves, because everything you produce looks identical in a row of pots and you will not remember by autumn which came from where. Label every piece with the date and the method used, and keep a short note of how many pieces you started and how many were still growing a month later.

Two seasons of that tells you something genuinely useful about your own conditions: whether your offsets survive better than your cut corm sections, how long a runner really takes to root for you, and which spring week gave the strongest plants. It also tells you when a parent plant is producing fewer offsets than it used to, which is usually the first sign that it needs dividing, feeding harder, or a bigger pot.

Wear gloves for all of this. Cutting into corms and runners releases sap that stings skin and burns badly on contact with eyes or lips. Wash your hands and your blade when you finish, and keep the pieces away from pets, since the whole plant is toxic if chewed.