The onion, one of the oldest vegetables used by the mankind, is a culinary ingredient in almost every dish, raw or cooked. Revered by the ancient Egyptians for its spherical shape and concentric rings, which were considered a symbol of eternal life, the onion is known for its wide range of medicinal properties. It is believed to have anti-inflammatory, antioxidant, and anticancer properties. It is a rich source of vitamin C, chromium, and flavonoids. With a characteristic pungent smell imparted by its high sulfur content, onions can accentuate the taste and flavor of any dish. It is not very difficult to cultivate onions, if you provide them the optimum growth conditions, which are discussed below.
Onions can be grown in almost all types of soil, like sand, loam, or clay soil. But the most important thing to be considered is that the soil should be firm and well-drained, i.e., it should be moist, but not soggy. Good drainage is a prerequisite for growing onions. Onions generally grow well in acidic soil having a pH between 5.5 to 6.5. You should select a plot which gets sufficient sunlight, preferably for 6 hours a day. Adequate soil moisture is also important for growing onions.
To prepare the land for onion cultivation, you have to till it properly. As composting helps improve the soil, manure or organic compost can be added to it. Fertilizers can also be used, but those that are high in nitrogen are not suitable. Such fertilizers can promote the growth of small bulbs with green, overgrown tops. Manure or organic compost should be added a few weeks before sowing the onion seeds. You can also moisten the soil with water a day before sowing. To make the soil firm, tread on it gently.
You can either opt for seeds or onion sets. An onion set is a small, partly grown dormant onion. Sets have certain advantages over seeds, as they can be grown quickly and they require less skill and labor. If you are planning to grow onions from seeds, then sow them about 2 cm deep into the soil. Remember to keep a proper distance between seeds, usually a distance of about 1 inch. If you are going to grow them in rows, the distance between two rows should be about 30 cm. The row distance also needs to be maintained, if you are planting onion sets. However, the sets should be planted 10 to 11 cm apart.
Seeds would usually take 2 to 3 weeks to germinate. Once the seedlings reach a height of 5 cm, they would require thinning. While thinning, place them around 3 to 4 inches apart to avoid crowding. Providing the required amount of water is important in onion cultivation. Watering once a week would be sufficient till the tops begin to fall or become yellow, which indicates that the bulbs are about to reach maturity, and so, watering can be stopped.
Onions can also be grown in a soilless potting mix. The soilless potting mix does not contain soil, but various other ingredients like peat moss, composted pine bark, sand, perlite, vermiculite, small amounts of limestone, and other minerals or fertilizers. To grow vegetables in such a mixture, seeds should be sown approximately ¼ inch deep into the soil, and covered with the soilless potting mixture. They should germinate in about 2 weeks, after which they can be grown in peat pots or cell packs. When they reach a diameter of about ¼ inch, they can be planted in a vegetable garden.
Nowadays, several varieties of onions are available, and they can be grown in different seasons. For example, the maincrop onion seeds or sets can be sown from late February to early April, while salad or spring onions can be grown from March to July. The Japanese variety of onion can be planted in early September.
The maturity of the onion bulbs is indicated by the color and size of the tops. When the tops turn yellow or begin to fall, it indicates that the bulbs are approaching maturity. Harvesting is usually done, when the top reaches a height of around 6 inches, or a week after the tops turn yellow or start falling off. While harvesting, one should be careful not to damage the skin of the onions. The skin protects the flesh from certain organisms that attack and decay the flesh. So, lift the onions gently without damaging the skin, and remove the soil from their surface. You can keep them above the ground for a few days till the tops dry out. Then remove the tops from the bulbs. Generally, sunny days are ideal for harvesting onions.
Onion cultivated sites are often invaded by undesirable weeds. Weeds can hamper the growth of onions, especially the young seedlings, as they grow very slowly. Many herbicides are available in the market, but their excessive use can damage the onion plants. Therefore, frequent removal of weed or weed control is essential to facilitate the proper growth of onion plants.