Many gardeners prefer to grow their onions from seed because they have a finer flavor than onion grown from sets and may keep better. Start seeds indoors in January or February. Onions do best in fairly rich, light, well-drained loam-doesn't like clay or acid soils. Harvest when the tops begin to dry up and fall over.
Selecting Onion Varieties for your area:
Have you ever planted onions from seed and gotten tops but no bulbs?
The formation of an onion bulb is triggered by daylength, which varies according to how far north your garden is, since daylength increases with latitude. Onions that bulb best in the north are called "long day" onions, and need 14 -16 hours of sunlight during the summer to begin to form their bulbs. Our long-day varieties are New York Early, Southport White or Red Globe and Walla Walla.
In between are the "intermediate day" onions, most widely adaptable, requiring 12-14 hour days to make good-sized bulbs. Our intermediate varieties are Red Torpedo, Ailsa Craig and Giant Zittau. The Ailsa Craig, Valencia and Giant Zittau are often called "day-length neutral" because their range of successful latitudes is fairly broad.
Varieties that are better for southern states are called "short day" onions, and need 10-12 hour days to begin bulb formation. Our short day varieties are Red Torpedo, Southport White or Red Globe.
In addition, the size of the bulb is related to the number and size of the green leaves present when the formation of the bulb begins, so it's best to get an early start with onions so that the plants are of a good size when bulbing begins. In our gardens here in Willits, onion seeds are started in flats in mid-January, the earliest vegetable crop to be started in the new year, the beginning of the annual planting cycle.