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Information from Texas Cooperative Extension and Grayson County Master Gardener Program
Backyard gardeners can start onions from small bulbs, called transplants or sets. These can be planted now, as onions are a cool season plant, but may need covering if temperatures are well below freezing. Onions can also be grown from seed, but seeds must be planted in the fall, October through December, as a longer growing time is required.
The Texas Cooperative Extension recommends that the garden soil be spaded or tilled to a depth of 8 or 10 inches. Then spread 2 to 3 pounds of 10-10-10 fertilizer for 100 square feet of garden and work into the top 3 to 4 inches of soil.
Sets or transplants should be planted ¾ - 1 inch deep and 3 inches apart. Do not mound soil up around the plants as bulb develop, as this can cause stem rot. Water slowly, about once a week, to help develop strong roots. More frequent watering may be needed when the weather is dry and windy, less during wet spells. The goal is for soil to be moist, but not soggy. Weed regularly, as weeds compete with the onions for nutrients.
Apply fertilizer a second time, when plants have developed five to six leaves. Each leaf forms a ring in the onion bulb, so the more leaves, the larger the onion. Use about a half cup of 10-10-10 fertilizer for each 10 foot row, and water it in.
Onions planted now should produce bulbs in May to July, or they may be picked as green onions once they reach pencil size. For dry bulb onions, gardeners can begin to harvest when the main stems grow weak and about 2/3 of the tops have started to fall over. Pull or gently dig the bulbs out of the soil and lay them in the garden for a day or two to dry. Avoid bruising, for longest storage life. Continue drying by removing roots and placing in a basket or box, out of direct sunlight. Plastic trays used for flats of plants are good for this purpose. Tops may be left on, or cut off an inch above the bulb,
Once dry, store in refrigerator crisper or hang in net bag in airy place. Nylon stockings can used for storing onions, with a knot tied between each bulb. Onions with tops left on may be braided also, for hanging.
The County Extension office has free publications and expert gardening advice, available by visiting the Grayson County Courthouse or calling 903-813-4206.