Like most gardeners, I started out growing onions from sets, which are small, immature onion bulbs. They were easy to grow, and I soon wanted to expand my variety horizons, but with onion sets, choices were limited. So, I turned to seeds. Growing from seed let me pick varieties to suit my own needs or whims - such as the desire for an early-season sweet onion or a late-season keeper. Colors range from dashing purple to pure white and numerous shades of yellow. Shapes and sizes vary, too, from the bottle-shaped "Italian Torpedo" to the plump perfection of "Ailsa Craig Exhibition."
Most onion experts agree that, diversity aside, onions grown from seed perform better than those grown from sets. They are less prone to disease, they store better, and they bulb up faster.
Onions need a long growing season, so place your seed orders early to get a head start. On a cold winter night, it's great fun to browse through those seed catalogs piling up beside the sofa and choose a few new varieties.
When choosing seed, make sure to order types suited to your climate and zone. Long-day onions are best grown in the North, where the summer daylight period is longer. These onions require at least 14 hours of light to bulb up. The plant grows foliage in cool spring weather, then forms bulbs during warm summer weather, triggered by the long days.
To grow onions from seed, simply sow seeds quarte-inch deep in flats filled with soilless potting mix in late February. Onions germinate in just a week at around 70 F. Once the seeds have sprouted, I grow my onions under fluorescent lights, one warm white and one cool white bulb per fixture. I keep the lights just above the leaves, adjusting the lights as the plants grow.
I feed the seedlings with a water-soluble fertilizer at half strength every other time I water, being careful not to keep them too wet. I also keep the onions trimmed to be about 4 inches tall, so that the plants focus on root growth. Finally, I thin them to one every quarter-inch or so. By mid to late May, the onions are ready to be planted outside!
Anne Lenox Barlow has had experience in the agricultural field as a horticulture educator with Cornell Cooperative Extension in Clinton County. She can be reached by e-mail at firstname.lastname@example.org.