Easy to cultivate with a long storage life, backyard gardeners are growing onions (Allium cepa) successfully in most areas of the United States. We rely heavily on these glorious globes for their sweet to pungent flavor and enjoy them fresh, dried or cooked in a number of dishes including salads, soups and souffle.
Onions are so popular, it’s easy to forget that the plump bulbs serve up a super-sized portion of vitamin C, they’re low in calories, and are high in minerals and dietary fiber. Other wellness benefits include cardiovascular health and cold and allergy prevention.
Fun Fact: Records indicate that onions were grown in Ancient Egypt, and eventually arrived in Rome and became known as the word onion (from the Latin word UNIO, which means large pearl).
Sow onions indoors up to twelve weeks ahead of outdoor transplanting.View all
Starting from seed is often the only way to get classic, gourmet heirloom onions. Planting instructions are included with each seed packet and shipping is FREE!
Quick Guide: Planting, Growing & Harvesting Onions
- Choose a variety suited to day length in your areas (see above)
- Direct seed or plant sets
- Plant into well-prepared soil in full sun
- Keep well watered, fertilize regularly
- Harvest by pulling bulbs and drying them for 2 weeks
- Common pests and diseases are thrips, wireworms, botrytis rot and downy mildew
Onions grow best in full sun and deep, fertile, well-drained soil with plenty of organic matter. Work in a generous amount of organic compost or well-aged animal manure prior to planting. All varieties are shallow rooted and need constant moisture near the surface.
Bulbs form in response to day length. If you choose a type inappropriate for your area, it may make small, premature bulbs or no bulb at all. Long-day varieties, Sweet Spanish included, need 14-16 hours of daylight and are grown in northern climates. Short day varieties, Bermuda included, need 10-12 hours of daylight. These start making bulbs early in the year. Select an onion type that is suited to your zone for best results.
How to Plant
Starting from seed is often the only way to get classic, gourmet varieties. Sow indoors up to twelve weeks ahead of outdoor transplanting. Set out two weeks before last frost. You can also purchase sets from nurseries and garden stores. Sets are easy to start and mature quickly, but varieties are often limited.
When planting onions allow 2-4 inches between seedlings in traditional rows spaced 1-2 feet apart. Mulch and weed thoroughly. Feed young plants with a high quality organic vegetable fertilizer and apply Liquid Fish & Seaweed later in the season to improve crop yields, taste and appearance.
Harvesting and Storage
Onions are ready to harvest when the tops fall over naturally, usually 80-100 days after direct seeding; 30-40 days from sets. Pull bulbs from the ground and let them air-cure for two weeks. Watering prior to harvest makes pulling easier.
After curing, store the bulbs in a cool, dry place such as the cellar. Do NOT keep in a plastic bag.
Insect & Disease Problems
To prevent insect and disease problems rotate crops and avoid planting onions in the same area for three years. Thrips are suspected if the bluish-green leaves become bleached and wither. Damage to the lower portion of the stem is often caused by onion maggots. Wireworms (the larvae of click beetles) can also cause serious damage as they feed on all underground parts.
Note: Monterey® Take Down Garden Spray combines the fast knockdown of pyrethrin and the residual activity of canola oil to kill ALL stages of insects, including eggs. Best of all, it breaks down quickly in the environment and may be used on edible crops up to and including the day of harvest.
Seed Saving Instructions
Biennial. Plants cross-pollinate and should be isolated by 1 mile from other onions going to seed. Select only the best bulbs and store 3-6 months at 32-45˚F. Plant out bulbs in early spring and allow them to form seed heads. When the heads start to dry, cut off the tops, dry further and thresh.
Sup'r Green provides over 5 times more plant food value than steer manure.
Hand-crafted to improve the yields, taste and nutrition of vegetable crops.
Take Down Spray
Combines the fast knockdown of pyrethrin and the residual activity of canola oil.
Handmade in Maine from quality hard and soft woods and lobster trap wire.