Published March 16th, 2010
It seems too early to be vegetable gardening, but experienced gardeners have their onions in the ground by St. Patrick’s Day. Onions and shamrocks are perfect together! In order to get fat onion bulbs, you need to grow big healthy tops before the days get long. That’s when the plants switch from growing foliage to storing food in the bulbs, so planting too late means puny bulbs at harvest time.
The easiest way to grow onions in the home garden is by planting onion “sets”, tiny onions that grow into big onions. We sell these by the pound in yellow, sweet white and sweet red. Look for onion sets that are fat, shiny and firm. Soft or moldy sets won’t perform as well.
All you need to do is loosen up a patch or row with a cultivator, mixing in some 10-10-10 fertilizer, and then press the little onions into the loose soil two inches deep and two inches apart. We recommend “wide row” planting; instead of a single line plant six or eight rows a few inches apart. Onions don’t mind being crowded, and later you can thin the weaker plants and have plenty of fresh scallions. Make sure to tamp the soil over your onion sets.
Onions need fertilizer three or four times before harvest. Use 10-10-10, sprinkling the fertilizer around the base of the plants (fertilizer dust can scorch the foliage). Super-phosphate and bone meal are good for onions too. Fertilize when plants reach 6 inches, and again 3 or 4 weeks later. The best way to fertilize onions is by “side dressing.” This means sprinkling fertilizer at the base of the plants, taking care not to get fertilizer dust on the stalks, where it can burn.
Thin every other plant, harvesting the weaker ones. Big, healthy tops mean big fat onions. Pinch off any seedpods, because if the plants set seed they won’t grow big bulbs. Once the days are long enough, healthy vigorous onion plants “shift gears” and energy from the big tops is transported down to make a bulb. Bulbs continue to grow until the tops wither and turn brown. That’s the best time to harvest.
If your garden is too gooey to plant, try making some fluffy dirt just in the onion rows: Sprinkle 10-10-10 fertilizer and a little superphosphate on the row and then spread three inches of peat moss. Till the row six inches deep, trying not to step on the freshly tilled dirt. Rake it smooth. Magic. Now you can tuck in your onion sets easily. Next tamp the soil gently. You’re done, and right on St. Patrick’s Day schedule!