Short Day, Long Day and Day Neutral Onions
Maximize your onion harvest by selecting the variety suited to the daylight hours in your region.
Onions are photoperiodic, meaning they are influenced by the length of daylight. Short day onions form their bulbs when days are 10 to 12 hours long. They’re planted in fall in zones 7 and warmer for a late spring harvest. Northern gardeners can plant them in spring along with their other vegetables, but the bulbs will be much smaller.
Long Day onions need 14 to 16 hours of daylight to form their bulbs. These are popular in zones 6 and colder where they are planted in late winter or early spring.
Day neutral onions form bulbs with 12 to 14 hours of daylight. They’re ideal for zones 5 and 6 but work well in all regions except South Florida and South Texas. Plant these in fall in mild climates and early spring in colder regions.
A bit more information: Onions can be started from seed, transplants or sets. Transplants are often sold in bare root bundles or as plants growing in cell packs. Individual plants are separated and planted in the garden.