When the Onions Send up Flower Stalks

Many area gardeners who planted onions this year are looking out over onion patches that are punctuated by flowering stalks, also called seed stems. The onions will still be good.to eat, but this condition does reduce the keeping quality and ultimate size of the mature bulbs.

Unfortunately, the same problem is affecting onions in Georgia's best-known onion-producing region.

An article in the 2 May issue of UGA's Family, Agricultural, Consumer and Environmental Sciences newsletter,  Fluctuating Weather Patterns Reduces Vidalia Onion Crop Yields, includes a note about how many of this year's Vidalia onions have developed the seed stem condition:

"In some farmers’ fields, upwards of 70 to 80 percent of the onions had seed stems, said Reid Torrance, a Vidalia onion expert with University of Georgia Cooperative Extension who has been serving the Tattnall County onion-producing area since 1984."

Mr. Torrence has more to say about this year's abundance of seed stems:  “It’s hard to pin down exactly what triggers the onions to develop seed stems,” he said. “But I think these huge fluctuations in temperatures we had this year contributed to it. Anything that shocks the plant can cause it to develop a seed stem.”

Clemson University's Onion, Leek, Shallot & Garlic publication agrees with Mr. Torrence's statement about the probable cause for this condition:

"Onions will bolt (produce a flower stalk) if exposed to a prolonged cold period following a favorable growing period. This results in small bulbs with large necks which are hard to cure and generally unusable. The larger the plants are at the time of exposure to the cold period the higher the rate of bolting.

To help prevent bolting:

• Select onion sets of an inch or less and transplants about 6 inches high and about half the thickness of a lead pencil.
• Plant at the correct time for your area.
• Avoid high fertilizer rates applied in the fall."

Many gardeners believe that trimming off the flowering head of the seed stem will result in larger onions than if the heads are left, but the Texas Aggie Horticulture publication Growing Onions  has this to say about cutting off the flowering stalks:

"What can one do if flower stalks appear? Should the flower stalks be removed from the onion plants? Suit yourself but once the onion plant has bolted, or sent up a flower stalk, there is nothing you can do to eliminate this problem. The onion bulbs will be edible but smaller. Use these onions as soon as possible because the green flower stalk which emerges through the center of the bulb will make storage almost impossible."

Normally, storing mature, harvested onions in a cool, dry, dark area is enough to keep them good for several months, but onions affected by seed stem will not keep for very long even under optimal storage conditions.
Gardeners who have a fairly large crop of affected onions may want to share them with neighbors and friends so they can be used while they are still good.

Alternatively, the National Center for Home Preservation offers information on blanching and freezing onions for later use excerpted from UGA's wonderfully helpful book So Easy to Preserve.