Growing Onions

OnionsEasy to cultivate with a long storage life, home gardeners are growing onions more than any other vegetable! Records indicate that they 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).

Site Preparation:

Onions grow best in full sun and deep, fertile well-drained soil with plenty of organic matter. Work in a generous amount of compost prior to planting. Onions are shallow rooted and need constant moisture near the surface.

Onions form bulbs in response to day length. If you choose a type inappropriate for your area, it may make small premature bulbs or not bulb up 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 that is suited to your zone for best results.

How to Plant:

You can grow onions from seed, seedlings or sets. Sets mature quickly and are easy to grow, but varieties are limited. Seed should be sown in the fall to set bulbs in spring or summer.

Allow 1-4 inches between plants in traditional rows spaced 1-2 feet apart. Feed the plants, especially early in the season, with a low nitrogen organic fertilizer.


Allow tops to fall over naturally, then pull bulbs 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. Onions reach maturity 80-100 days after direct seeding; 30-40 days from sets.

Insects and Diseases:

To help prevent insect and disease damage avoid planting onions in the same area for three years. Damage to the lower part of the stem is often caused by the onion maggot. Thrips are suspected if onions becomes bleached and wither. Wireworms (the larvae of click beetles) can also cause serious damage as they feed on all underground parts.

Note: 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.

Common diseases include botrytis rot and downy mildew, both of which are characterized by soft tissue and mold.

Seed Saving Instructions:

Biennial. Onions 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 degrees F. Plant out bulbs in early spring and allow them to form seed heads. When the heads start to dry, cut off, dry further and thresh.

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