Garden Vegetable - Onions, Green

Botanical Information

Starting

Notes:

Prefers a sunny sheltered location in a rich light well-drained soil. Prefers a pH of at least 6.5 and will tolerate a pH in the range of 4.5 to 8.3. Onions are best grown in a Mediterranean climate, the hot dry summers ensuring that the bulbs are ripened fully. For best growth, however, cool weather is desirable at the early stages of growth. Plants are frost-tolerant but prolonged temperatures below 50°F cause the bulb to flower. Optimum growth takes place at temperatures between 68 and 77°F. Bulb formation takes place in response to long-day conditions.
Plants are perennial but the cultivated forms often die after flowering in their second year though they can perennate by means of off-sets. The onion was one of the first plants to be cultivated for food and medicine. It is very widely cultivated in most parts of the world for its edible bulb and leaves, there are many named varieties capable of supplying bulbs all the year round. This species was derived in cultivation from A. oschaninii. Most forms are grown mainly for their edible bulbs but a number of varieties - the spring onions and everlasting onions - have been selected for their edible leaves. Onions grow well with most plants, especially roses, carrots, beet and chamomile, but they inhibit the growth of legumes. This plant is a poor companion for alfalfa, each species negatively affecting the other. Members of this genus are rarely if ever troubled by browsing deer.

Propagation: Seed. Early sowings can be made in February in a greenhouse to be planted out in late spring. The main sowing is made in March or April in an outdoor seedbed, this bed must be very well prepared. A sowing can also be made in an outdoor seedbed in August of winter hardy varieties (the Japanese onions are very popular for this). These overwinter and provide an early crop of onion bulbs in June of the following year.
Onion sets can be planted in March or April. Sets are produced by sowing seed thickly in an outdoor seedbed in May or June. The soil should not be too rich and the seedlings will not grow very large in their first year. The plants will produce a small bulb about 3/8-7/8 in in diameter, this is harvested in late summer, stored in a cool frost-free place over winter and then planted out in April. A proportion of the bulbs will run quickly to seed but most should grow on to produce good sized bulbs.