zone 8 onions
zone 8 onions
(Image credit: YuriyS)

Onions have been cultivated all the way back to at least 4,000 BC and remain a major staple in almost all cuisines. They are one of the most widely adapted crops, growing from tropical to sub-arctic climates. That means that those of us in USDA zone 8 have plenty of zone 8 onion options. If you’re interested in learning about growing onions in zone 8, read on for more information about onions for zone 8 and when to plant onions in zone 8.

About Onions for Zone 8

The reason that onions are so adaptable to many different climates is due to differing responses to day length. With onions, day length directly influences bulbing rather than flowering. Onions fall into three basic categories based on their bulbing related to the number of daylight hours.

  • Short day bulb onions grow with day lengths of 11 to 12 hours.
  • Intermediate onion bulbs require 13 to 14 hours of daylight and are suited to the mid-temperate areas of the United States.
  • Long day varieties of onion are suited to the most northern regions of the United States and Canada.

The size of an onion bulb is directly related to the number and size of its leaves at the time of bulb maturity. Each ring of the onion represents each leaf, the larger the leaf, the larger the onion ring. Since onions are hardy to 20 degrees F. (-7 C.) or less, they can be planted early. In fact, the earlier an onion is planted, the more time it has to make more green leaves, thus larger onions

Onions need about six months to fully mature. This means that when growing onions in this zone, all three types of onions have the potential for growth if they are planted at the correct time. They also have the potential to bolt if they are planted at the wrong time. When onions bolt, you get small bulbs with large necks that are hard to cure.

When to Plant Onions in Zone 8

Short day zone 8 onion recommendations include:

  • Early Grano
  • Texas Grano
  • Texas Grano 502
  • Texas Grano 1015
  • Granex 33
  • Tough Ball
  • High Ball

All of these have the potential for bolting and should be planted between November 15th and January 15th for harvest in the late spring to early summer. Intermediate day onions suited for zone 8 include:

  • Juno
  • Sweet Winter
  • Willamette Sweet
  • Midstar
  • Primo Vera

Of these, Juno is the least likely to bolt. Willamette Sweet and Sweet Winter should be planted in the fall and the others can be planted or transplanted in the spring. Long day onions should be set out from January to March for a late summer to fall harvest. These include:

  • Golden Cascade
  • Sweet Sandwich
  • Avalanche
  • Magnum
  • Yula
  • Durango
Amy Grant

Amy Grant has been gardening for 30 years and writing for 15. A professional chef and caterer, Amy's area of expertise is culinary gardening.