Green gardening: Growing onions

The homegrown version of the common "globe" onion is not noticeably superior to the commercially raised product so home gardeners often don’t plant them. Scallions or green onions are more flavourful and also take up less space in the garden.

Onions need fertile, carefully worked, moist soil with good drainage. They can be replanted for several years in the same spot, so it is worth the effort to prepare a good bed for them. Work in one kilogram (two pounds) or more of well-rotted manure or compost for every one and a half metres (five feet) of row. If your soil is heavy clay or slow to drain, make raised planting beds.

Globe onions are hardy vegetables, and their seeds can be planted in the garden in early spring. Most home gardeners plant onion "sets," or small bulbs, because this shortens the time to maturity by four to six weeks and is more reliable than starting the plants from seeds. Where the ground freezes no more than one centimetre (half an inch) deep, onions can be planted in the fall for spring harvest.

• Onion sets. Onion sets are sold by weight; 250 grams (nine ounces) will fill a seven-metre (22-foot) row. The bulbs should be no larger than one centimetre (half an inch) in diameter, or they may run to seed before producing edible onions. Plant onion sets when ground can be worked. Place them 10 centimetres (four inches) apart, three centimetres (one inch) deep, in rows 30 centimetres (12 inches) apart.
• Seedlings. Garden centres also carry onion seedlings; plant them in the same way as sets. If you are starting globe onions from seeds, sow the seeds three centimetres (one inch) apart and one centimetre (half an inch) deep. When the seedlings are eight to 10 centimetres (three to four inches) tall, thin them to stand five centimetres (two inches) apart. When the seedlings reach 15 centimetres (six inches), thin them to stand 10 centimetres (four inches) apart.

• Watering. Globe onions have shallow root systems, and therefore need frequent watering.
• Weeding. Careful weeding is needed. To keep the weeds down, hoe shallowly between rows; within the rows pull out the weeds by hand.
• Fertilizing. The plants will also need additional fertilizer while they are growing. When they are 20 to 25 centimetres (eight to 10 inches) tall, spread a band of compost along both sides of each row. You can also apply a liquid fish fertilizer solution once a month.

• Globe onions are ready for harvest about five months after seeds have been sown or three and a half months after planting out sets or seedlings.
• The onion tops wither as the bulbs reach maturity, turning yellow and then brown. You can speed up the maturation process — and produce larger bulbs — by bending the tops over when the outer leaves turn yellow.
• Two weeks later loosen the bulbs by pushing a spading fork beneath them and lifting them slightly.
• In another two weeks lift out the bulbs with the fork. You can either cut the tops off a little above the bulb or leave them on for braiding after the onions have dried.
• Spread the bulbs in a warm, airy place for a few days until they are completely dry.
• Then braid them and hang them up; or hang them up in mesh bags; or store them loosely in shallow, open boxes. The storage area should be cool and moderately humid.