The underground stem (a bulb) of this pungent, strong smelling plant has been extremely popular for many centuries. Today there are two main types of heirloom onion seeds that interest the gardener. They are the (1) young, green or white, bunching sorts that are eaten fresh before the mature bulb has formed. (2) The other and much more widely grown sort develops a large, coated bulb with papery skin. Onions fed the sweating pyramid builders and the conquering troops of Alexander the great. General Grant in dispatch to the War Department wrote, “I will not move my armies without onions.”
Raising Heirloom Onions from Seed
There are three ways of raising heirloom onions: by seeds, by sets, and by multipliers or potato-onions that often develop among the flower clusters. When sowing heirloom onion seeds there are three times onion seeds can be sown: late summer, winter, and spring. Most areas of the U.S. typically will sow there heirloom onion seeds in late summer. The idea of planting your heirloom onion seeds in late summer is to get the onions to form bulbs by early spring, before hotter weather causes them to bolt, and then allow them to mature through the summer. Sow the heirloom onion seeds thinly in shallow drills, cover with an inch of compost and firm the ground. If the winter is particularly hard, put cloches out during the worst of it. In the spring, thin out the onions to about six inches apart. The thinning can be used in salad.
Care While Growing Heirloom Onion Seeds
Do not let onions go dry; they are shallow rooted and need moisture fairly near the surface. Also feed plants, especially early in the season: the larger and stronger the plants grow, the larger the bulbs they form. It is important to carefully eliminate weeds that compete for light, food, and water. When most of the tops have begun to yellow and fall over, dig bulbs and let them cure and dry on top of the dry ground for several days.
Soil and Climate
Heirloom onion seeds need good rich soil. Sandy loam, peat and silt are all fine, but onions do not like clay, sand or gravel. They grow successfully in widely different climates, although they prefer cool weather while their leaves are growing and developing followed by very much hotter weather while they make their bulbs. Before planting out, firm the ground by treading or rolling or both. The soil must be dry, whether you are sowing seed or transplanting.
Harvesting and Storing
When bulbs are ripe, the tops begin to yellow and fall over. When about ¾ have fallen, use a rake to break over those still standing. When all the tops are dead, pull up the plants and spread them in the sun for 3-4 days. Place the tops over the bulbs. Then cut the tops off about an inch from the bulb. It is vital to dry onions well. When they have dried, the best thing to do is string them. Otherwise, put them in layers in some cool, airy place. They must not suffer severe frost, but it is better for them to be cool rather than hot.
Pests and Diseases
Onion fly: the maggots of the onion fly are one of the nastiest pests we have to suffer from as they can stop onions growing altogether. The maggots eat into the bulbs of seedlings. Spring sown onions are the worst hit, but onions grown from sets are not likely to be affected. To deter onion flies and their maggots dust your rows of onions with flower sulfur. Dust fairly regularly, particularly when you thin the plants.
Heirloom Onion Varieties
White Sweet Spanish – Mild, sweet and tasty. White fleshed and has a thin neck. Good winter keeper. Produces fruits weighing up to 1 lb.