How to Propagate Onion

Allium cepa

Onions are most commonly grown from small bulbs called “sets” rather than seed, since sets establish faster and more reliably than starting from seed for most home growers.

Division (sets)

1. Plant small onion sets (immature bulbs) an inch deep, pointed end up, spaced several inches apart.
2. Keep consistently moist while establishing.

Green shoots emerge within 1–2 weeks; bulbs mature over the growing season.

Growing from seed

Sow indoors 8–10 weeks before the last frost for a head start, since direct seeding takes considerably longer to reach harvest size.

When to propagate

Spring, as soon as the soil can be worked.

Common problems

Sets rotted instead of sprouting. Soil too wet — ensure good drainage.

Questions people ask

Can I regrow onion from a store-bought bulb’s root end? You can get some green regrowth similar to green onion, but it won’t form a new full bulb the way a set will.

Is onion toxic to pets? Yes — the whole onion family is toxic to cats and dogs if eaten, even though it’s safe for people. Keep sets and trimmings away from pets.

Related

Similar plants: Garlic, Green Onion