The Q&A Archives: Onions are double-bulbing

Question: Each year a large portion of my Dutch storage onion sets develops double bulbs two separate onions on one root. Why is that? Raymond Casciotti Altoona, PA

Answer: It's mostly a varietal problem, says Mike Orzolek, vegetable crops specialist at Pennsylvania State University in University Park. Dutch onion sets are stressed when temperatures go above 90oF early in the season. An onion bulb is actually a modified stem, so any stress to it will cause a dormant onion bud to begin to grow. This results in a second bulb forming on the same root system, Orzolek explains. You can avoid this problem by choosing storage onion varieties that are better adapted to our weather, such as Spartan Banner, Sweet Spanish and Stuttgarter, he suggests. If you can't find these varieties locally as onion sets, I'd suggest starting them indoors from seed, says Orzolek. Sow the seed under grow lights the first week of February and keep the tops trimmed to four inches in height. Transplant the onions into the garden by April 15. To get good size on the bulbs, keep the transplants evenly moist (water at least once a week) and weed free, especially early in the season, Orzolek recommends.

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