Three Ways to Start Onions: Seed, Transplants and Sets

Bulb onions are planted and grown from seeds, transplants, or sets. Transplants are live seedlings, often bare rooted, and often sold in bundles of about 25 plants. Sets are small, dormant onion bulbs grown specifically to give gardeners and farmers a head-start on the growing season, often sold by the pound or in preweighed mesh bags.

Buying and growing bulb onions successfully from transplants and sets can be tricky. GardenZeus recommends growing your own starts or seeding directly outdoors in fall. Short-season varieties that are ideal for many portions of California are not sold as sets. You may find them as transplants (live plants) at local nurseries, online, or by mail order from about September through November each year. Short-season transplants are sold as non-dormant plants. They are actively growing bare-rooted onions, and should be planted promptly; unlike dormant sets, they will not keep for long if unplanted.

Many local nurseries in the warm inland valleys of California offer bulb onion sets in late winter and early spring. These are often long-day varieties such as Ebenezer White (mild when young, pungent at maturity), Yellow Rock (mild flavor and stores well), and Wethersfield Red or Dark Red Beauty (mildly pungent), which are adapted to growing in the northern United States, and do not bulb well in most portions of California. They will never form the large, full bulbs that you might see on their nursery packaging because of the short day length. Onions grown from sets also tend to bolt early in response to either cold or hot weather.

For a discussion of the importance of day length when selecting onion varieties see Selecting Onion Varieties for California Gardens: The Importance of Day Length. For a complete, customized information for growing onions in your area, go to GardenZeus and input your zip code.