by Thomas N. Tomas
Onions may be grown from seeds, sets, or plants. Actually, they all begin as seeds. Onion sets are grown from seed which is sown thickly the year before and allowed to grow to the size of a large marble. They are then harvested and stored until the following spring, when you buy them as sets. Onion plants are started from seed, usually down south, and then grown to about the size of a pencil before they are pulled, tied into bunches and offered for sale. The seeds develop in the summer after a white ball of flowers ripens on top of a tall stalk that shoots up from the bulb.
If you sow the seeds directly in the garden in very early spring, you can expect good sized onions by August or September. This works well if you want the greatest selection of varieties and are willing to weed the tiny plants when they come up. The earlier you plant the seed the bigger the onions will get, as the size of the onion is determined by the number of leaves the plant produces before the day length begins to get shorter. I like to plant as soon as the soil can be worked at the end of February or in March. They will not come up until the soil warms up, but if we get an early spring they will be able to take advantage of it, even if the soil is too wet to work for planting later on. I plant about 12 seeds per foot of row and only thin the ones that are really thick, as they will grow and push each other out of the way as they need space.
Onion plants should be planted as early as you can get them in because the same rule applies - the number of leaves present when the days begin to shorten will determine the size of the bulbs, all else being equal. I space onion plants about 3 inches apart as they are somewhat expensive, and wider spacing makes it easier to control weeds. Select the freshest, greenest onion plants you can find for the best results. If they are brown and dormant they will take longer to get established. It is easier to grow big slicing onions from plants than from seed because they are easier to get started, and you can see where they are to start controlling weeds earlier.
Onion sets are the easiest way to grow green onions and small to medium sized onions for cooking. The selection is usually limited to only a few varieties that are best adapted for set production and storage. They can usually be found in red, white and yellow, with no indication of the actual variety. I like the taste of the red best with yellow a close second. To me the white onions are too hot for a green onion. Select only sound dry sets free from mold. They will usually range in size from one-fourth to an inch in diameter. Believe it or not, the smaller sets will usually give you the larger cooking onions. They are less likely to bolt, or go to seed, and therefore put more energy into growing a large bulb. When I plant onion sets, I alternate between large sets and small sets about an inch or two apart in the row. As the large sets grow and bolt to seed I pull them for green onions, leaving the smaller sets to grow into bigger bulbs that I harvest as needed later or store for winter.
Each year I usually grow a few storage varieties from seed, a sweet slicing variety from plants and green onions from sets. The sets are the most fun because they are so easy to plant, and they take me back to my first experiences in my father's garden where he would mark out the row and I would carefully plant the sets. Perhaps that is the best thing about sets. You can get your kids or grandchildren to help and almost certainly succeed.Nebraska Sustainable Agriculture Society: Home Gardening