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Most of the onion seed produced in central Oregon is for white and yellow onions, with red onions on occasion. Seeds are planted from late July to September if using the seed-to-seed method and planted from September-October if using the bulb-to-seed method. In the right environmental conditions an onion plant will form one or more flower inflorescences which terminate in an umbel that contains several hundred seeds. The process of the seed producing inflorescences is called, “bolting.” In order for bolting to occur, the plant must go through a period of chilling (45-55 degrees F) for one month or longer depending upon the variety. Onion seeds have to be pollinated, generally honeybees, so onion seed fields must be isolated by a minimum of 1 ½ miles from any other onion seed field to prevent cross pollination.
Seed maturity is reached and harvested by mid June to August of the following year. Mature onion seeds will naturally fall from the inflorescence if they are not immediately harvested so careful attention must be paid in order to figure out the correct time to harvest. They are generally harvested by hand, sometimes machine, leaving about six inches of stalk attached. Once they are transferred out of the field the stalks are laid out on tarps and dried for 2-3 weeks. After drying the umbels are thrashed using combines and the seed is then taken to a seed company’s cleaning facility where it is further cleaned and processed.
Over 100 acres of onion seed was planted and harvested in 2011, yielding 630 pounds an acre and grossing $819,000.