Agriculture & Natural Resources

Onions – alternative crop for Delaware?

Delaware onions Gordon Johnson
Gordon Johnson, UD Extension fruit and vegetable specialist

Onions. We cry as we slice them, but despite the tears, onions remain a favorite staple on salads, sandwiches and in stews. But can they be grown in Delaware? Yes, says Gordon Johnson, UD Extension fruit and vegetable specialist, but with some caveats for First State farmers.

For the past four years, Johnson has conducted trials on overwintering onions and spring transplants. Delaware’s unpredictable weather makes growing onions challenging, but not impossible.

University of delaware onion trial tour
Variety trial and field tours, like this onion tour, are held throughout the summer at the Carvel Center

Approximately 20 local farmers and growers attended an onion twilight tour, held at the research farm of the University of Delaware Elbert N. and Ann V. Carvel Research and Education Center in Georgetown, in order to see what’s up with the underground bulb. Red, white, or yellow, strong or sweet, growers are keen to grow what consumers like. Onions could provide a choice as an alternative crop, and a new opportunity for Delaware farmers.

Johnson’s research has traversed a good deal of trial and error, typically brought on by the unpredictability of Delaware weather. June is especially stressful, weather wise, and combined with weed and pest pressure, the swinging summer  temperatures can wreak havoc on the temperamental onion, which prefers a specific number of sunlight hours and a steady climate.  Although Delaware is “not a hotbed of onion production” investing in onions has potential rewards, Johnson said.

Onions have specific daylight requirements and are generally classified into two major categories, short day and long day. They are cultivated over two growing seasons, those planted in the spring and harvested in the summer, and onions that overwinter.

Planted in late summer or early fall, long-day onions grow better in northern locations. Long-day onions are characterized by a more pungent flavor and have better storage capacity, as long as six months or more, if properly stored in a cool, dry location, Johnson said.

Short-day onions, on the other hand, such as the consumer favorite Vidalia, thrive in southern climates and produce a sweeter bulb, albeit with limited storage shelf life. Short-day sweets are typically sewn from seed, or from transplants started in a greenhouse and planted by hand. These onions are harvested the same season they are grown.

Varieties of red, white and yellow onions are on display, together with signs that provide general results from the trials
Varieties of red, white and yellow onions are on display, together with signs that provide trial results

Strong shifts in temperatures, such as a cold snap in April or May, triggers an undesired “bolting,” the process by which an onion detects stress and flowers to reproduce. Johnson has pushed back planting dates to counteract the bolting sparked by a volatile Delaware spring. Johnson and his team keep a close eye on the varieties that are susceptible to bolting.

Not surprisingly, as a mid-Atlantic state, Delaware does best meeting the crop somewhere in the middle,  with a lesser-known intermediate-day onion. In Delaware, direct seeding of onions is difficult, Johnson concedes. “After four years of research I still can’t tell you when to sow,” he told his guests.

Onions grow well in rows of soil covered in plastic
Onions grow well in rows of soil covered in plastic

Onions grown from transplants fare better, and grow better in plasticulture – rows of mounded soil covered in plastic to reduce weeds and raise soil temperatures. For the past 10 years Pennsylvania and New Jersey have had good results growing onions in plastic, Johnson said.

For onions to be an attractive alternative crop for growers, farmers must commit to starting their own transplants from seeds or ordering transplants from southern suppliers, Johnson said. Growing transplants requires a lead time of 8-10 weeks before going into the ground in March. Farmers must be willing to invest in the higher energy costs to heat their greenhouses in January and grow enough onions to make it worth the investment.

plastic trays for growing onions
Johnson’s onion trials examine all types of seed and transplant trays for greenhouse productivity

Unlike other crops, growing onions cannot be automated. Johnson evaluates the seed trays – noting the best practice of sewing a single seed in one cell. The size of the cell tray, the number of cells per tray and labor to hand plant each cell or transplant in plastic rows are important economic and practical considerations, Johnson noted.

“Intermediate day onions reach their maximum size in June,” Johnson told growers, as he guided them through the various results of his trials. White onions do well in Delaware Johnson said, producing medium and jumbo sizes at a consistent rate.

A market for local onions exists, Johnson explained, and noted that local and frozen markets are in demand for the crop. Delaware onion growers could be poised to capture a short window in July and August when competing onions are not in season, Johnson added.

Johnson identified thrips as the major pests for onion. “Thrips will need to be kept in control if you are growing onions,” he said. “Lighter foliage color is more susceptible to thrips,” Johnson observed.

Norman Pierce, of Townsend, traveled south for a close up look at onions as an alternative drop
Norman Pierce, of Townsend, traveled south from New Castle County for a close up look at onions as an alternative crop

Delaware farmers Gwen and Norman Pierce traveled from their farm in Townsend, Delaware to attend the tour, their first visit at the Carvel research farm. Primarily goat farmers, Gwen Pierce said her husband devotes acreage to vegetables and is considering an alternative crop like onions. “We grow for local restaurants, “ Pierce said. ”My husband wanted to come here and check this out.”

Variety trial field tours, such as this onion twilight tour, provide an opportunity for growers and potential growers to taste, feel, smell and assess a potential crop. In addition to the information signage, attendees were given spring transplant and over wintering onion trial results. For more information visit the small vegetable and fruit resources.


Article by Michele Walfred
Photos by Michele Walfred and Jackie Arpie