Onions are one of the first crops gardeners get in the ground in spring. By late summer, green tops turn brown and flop over, signaling it’s time to harvest.
There is nothing worse than waiting all summer for your homegrown onions to mature, then discovering they spoil in storage. Selecting onion varieties well-suited for storage sets you up for success. Careful harvesting, proper curing and ideal storage conditions minimize storage losses and prolong the shelf life of onions up to 10 months.
Choose onion varieties well-suited for storage
Onion seeds are harvested from mature onion blossoms. It takes 2 years to grow a full-size onion from a seed. Onions sets are small onion bulbs. Gardeners plant sets in spring to grow full-size onions by fall. Onion sets are the fastest, easiest way to grow full-size onions in a single season. Planting sets also minimizes risk of rot.
Onions are classified by day length. Short day onions need 10 hours of daylight to develop bulbs. Long day onions need 14 to 16 hours. Day neutral onions develop bulbs regardless of light conditions. Long day and day neutral onions grow well in southern Ohio.
Choose onion varieties with a long shelf life. Plant breeders select traits to improve storability of hybrid varieties. Cortland and Copra are F1 Hybrids that keep well over winter.
Pungent onions are less susceptible to premature decay than mild tasting varieties because they have lower water content. Stuttgarter and Redwing onions are super sharp varieties with superior storability.
Harvest onions
Onions are ready to harvest when tops flop over and turn brown. Here in USDA hardiness zone 6, we harvest onions late summer through early fall.
It’s a good idea to dig a test onion to determine if your crop is mature. Look for a large, solid, well-developed bulb. Small immature bulbs don’t keep well in storage.
When harvesting onions, do not pull onions up by the greens. Pulling risks damaging greens, and leaves onions susceptible to rot. Instead, loosen soil around the bulb with a shovel, then lift bulb from earth by hand. Handle bulbs gently; bruised onions are more likely to spoil.
Cure onions
A period of dry curing is critical to preventing decay in storage. To dry cure, spread onions out in a warm, dry, well-ventilated place. Onions are sufficiently cured when their outer scales are brittle like paper and tops are completely dry (2+ weeks).
Storage
After curing, either clip tops to 1 inch above bulb and store in mesh bags or braid tops. Hang onions to encourage air circulation. Allowing air to circulate through onions prolongs shelf life.
Onions require cool, dry storage conditions with low humidity. A dark cellar or basement provides ideal storage conditions.
Thank you. My 1st yr to grow onions and had a big success. My only dark, cool room is an air conditioned attic room. Will this work?
Patti, As long as it stays relatively dry in your attic, you should be able to store your onions up there.