Most onions (Allium cepa) grown in home gardens are grown from onion sets or transplants. Onion sets are miniature onion bulbs grown the previous year and stored over winter for selling in early spring. Transplants are small onion plants grown in warm southern areas in late winter for selling in early spring. Growing onions from sets or transplants severely limits the choice of varieties for the home gardener. Growing onions from seeds offers the home gardener a larger choice of green (bunching), dry (storage) and sweet (fresh eating) onion varieties. Onions designated as "long day" are suitable for growing in the north and those designated as "short day" are suitable for growing in the south.
Green or Bunching
Tokyo Long White is a bunching onion with 12-inch long white stalks. It matures in just 65 days and will not form a bulb. White Spear matures in 60 days, producing thick, white 5- to 6-inch long stalks with an additional 6 inches of bluish-green leaves. This variety of bunching onion can overwinter as far north as USDA zone 4. A multipurpose onion variety introduced to the United States from Portugal in the eighteenth century, White Portugal can be grown as either a bulb or bunching onion.
One of the best onion varieties for long-term storage, Copra is a long-day onion suitable for growing in the north. Its yellow skin and white flesh is sweet due to its high sugar content. Copra matures in approximately 104 days. True to its varietal name, Candy onions are incredibly sweet and mild. A "day-neutral" variety, it is suitable for growing in either northern or southern gardens. Candy produces extra-large onions with a long storage life and matures in just 85 days. Red Burgermeister is a hybrid red onion that matures in 112 days.
The variety Walla Walla is considered the best variety of sweet onion for northern areas. It is a long-day variety that produces extra-large, globe-shaped bulbs with yellow skin and sweet white flesh. Walla Walla matures in 115 days. Yellow Granex hybrid onions are the same variety grown in the Vidalia onion-producing region in the state of Georgia, but only onions grown in this region can properly be called Vidalia onions. Yellow Granex is a short-day variety suitable for growing in the south and takes 182 days to reach maturity. It does not store well and is best eaten fresh.