When to Plant Onion Seeds
Growing onions from seed is a slightly different endeavor than growing from sets. Sets are more common, and produce a faster harvest, however there is significantly less variety available, and the harvest tends to be smaller, more susceptible to disease and do not store as well. Choose a variety of Onion that is best suited to your climate. Short Day onions are advised for southern climates, where they will grow through the cool Fall and Winter months and bulb production will be triggered when the days get longer in the summer. Long Day onions are best for northern climates, where they can enjoy the longer summer days necessary for them to form bulbs. Onions grown out of their ideal climate may never produce a useable, or good sized bulb.
Where to Plant Onion Seeds
Onion growers know that great onions come from well prepared soil. Onions need a sunny patch of fertile soil with good drainage. They prefer a pH of 6 to 7.5.
How to Plant Onion Seeds
For best results, onion seeds should be started indoors in flats and transplanted out of doors when seedlings are between 4-6 inches tall, taking care not to damage the roots. Onion seeds will germinate best in warm soil, between 68-75 degrees, with consistent moisture. When setting seedlings, actual root depth will depend on the length of root, but usually between 1.5 and 2 inches, making sure that most of the white of the stem is planted along with the root. Seedlings should be set at least 2-3 inches apart. Onions will thrive in moderate temperatures with consistent moisture. It is important to not let your onion plot dry out completely, this could stunt or even completely stop growth.
How to Harvest Onion
When bulbs have started to "fatten up," gently pull them out of the ground. If your plants have started to bolt, harvest and use immediately.