How do you plant and harvest onion sets?
—Margie Hawsey, Forest Hill, LA
Onion sets are easy to grow. They do best with at least six hours of full sun daily. Some gardeners plant them on a slight ridge, but that’s not necessary if the soil is light and well-drained. Plant onion sets high in the soil, just deep enough for the roots at the bottom to “catch.” Space them about 2 inches apart if you plan to harvest every other one early, or 4 inches apart if you let them all grow as large as possible before harvesting. Onions are biennials; they grow for a year, go dormant, then come back again the second year. At that point, they send up a flower stalk and produce seeds. When you buy onion sets, they’ve already grown their first year. When you plant them, they’ll grow larger, then they’ll flower and go to seed.
Remove flower stems that appear. The onions will continue to grow, and will usually send up more flower stems. You can either harvest onions in late summer while the greens are still healthy or wait until the greens dry naturally in fall. Be careful harvesting large onions you hope to store. Don’t bend and break the greens, as disease organisms can enter and rot the bulbs. Spread out onions with greens in a warm place to dry. Once the greens are dry and the “neck” at their base feels dry, store the onions in a cool, dry spot with good air circulation. They should store well for several months.