Growing Onions

Growing onions from sets (tiny bulbs) is probably the simplest method for the home gardener. The plants are quickly established and become vigorous and strong and may be used to produce both green onions and dry onion bulbs. But if your have your heart set on growing some really premium, large, dry onions (like those you see in catalogues) you'll need to start them from transplants. Transplants are purchased in bundles (usually 60 to 80 plants) from garden stores and through seed and nursery catalogs. One key thing you need to know prior to purchasing your transplants is which variety to buy and that is based on where your garden is located. Onions start bulb formation when the day length is of the proper duration and different varieties of onions require different day lengths to initiate bulbing. In general, most common varieties fall into one of three classes; a "short day" onion responds to 11 to 12 hours of daylight (south of the 35th parallel); an "intermediate day" onion needs 12 to 14 hours of daylight (in between the 35 and 37 parallel); and a "long day" onion requires 14-16 hrs (north of the 37th parallel). For this reason, onion varieties that are grown in the South are not adaptable to the North and vice versa. Onion varieties are listed as long-day, short-day and intermediate or day neutral by the store or catalogue when describing the variety. Make sure you purchase a variety that fits with the length of your longest days. Onions can be planted as soon as the garden can be worked in the spring, usually 4 - 6 weeks before the last frost date. In my mid-South garden, I plant them from February through April. They should be planted in well drained soil, 1-2 inches deep and 2 inches apart, thinning to 4-6 inches apart when the plants are 6 inches tall. You can use the thinnings in your early spring salads. Delicious!

Onions are shallow rooted and do not compete well with weeds so gently pull weeds around the developing bulbs. Fertilize with compost or a balanced organic fertilizer and keep soil evenly moist. Good fertility, adequate soil moisture and cool temperatures aid development.

Without some cool days, you will not get good top growth. The warmer temperatures will generate a larger bulb. As a matter of fact, the trigger to activate a large bulb is warmer temperatures and longer days. So the sooner you get them into the ground, the better your chances of getting the largest onions possible.

Onions will bolt, sending up flowers that will then form seedheads, as a reaction to ANY stress: being too cold, being too hot, having too much rain or having too little rain. Once an onion forms a stalk, it is 'done'. Removal of the stalk at that point generally does not encourage the onion to resume normal growth. Pull the plant and make whatever use of it you can.

Mature garden onions are ready for harvesting when the green top withers, falls over and starts to turn brown. This usually happens in mid to late summer. Be sure to harvest before the fall rains; mature onions will rot quickly in cool, wet soil. Lay mature onions in a single layer on newspaper in a warm, well ventilated place to cure for a few days. Leave undisturbed until the outer skin becomes papery and crispy dry. Select unbruised onions, rub off the stringy roots, and braid the tops. Hang in bunches or place in mesh bags and hang away from moisture. If stored in a dry cool place, they will keep for months.

If you plan on planting onions several years in a row, be aware that crop rotation is critical for continued success. Some onion diseases are partially controlled by rotation so never plant in the same spot more than once every 2-5 years. Thrips and onion maggots are the primary insect pests. Control thrips with insecticidal soap and onion maggots with crop rotations of 2 years, floating row covers to keep the adult flies from laying eggs on the fresh plants, or misting plants with water and dusting thoroughly with diatomaceous earth.