> The sweet onions we know today were descended from Bermuda onions, first brought to Texas in the late 1890s, according to Texas A&M University.
> Texas A&M’s Grano 502, a round sweet variety developed at the Winter Garden station, is often called the “mother of all sweet onions,” and is in the parentage of all super sweet onions.
> To develop “self pollinated” onions, researchers in the 1920s enclosed the bulbs in paper bags and tapped the bags every day to release the pollen.
> The original varieties of onions used to develop F-1 (granex) hybrids were the White Bermuda, Yellow Bermuda, Australian Brown and California Early Red, Frasier says. Practically all F-1 plants are self-sterile, meaning both male and female pollen is sterile.
> By 1960, 40% of all onions grown in the U.S. were hybrids. Nowadays hybrids are developed for disease resistance, maturity, color, shape and flavor.
> Dixondale Farms shipped its first granex transplants to Georgia in 1952.
> By their marketing order, Vidalia onions have to be a yellow granex type onion, meaning a flat onion. While there used to be only one variety out of Vidalia, there are now dozens, Frasier says.
> Walla Walla sweet onions are an open pollinated variety, so it is not a hybrid.
> Any sweet bulb with pyruvic acid of 3.5 µmoles/ml is very mild. One with 5 µmoles/ml is very strong.
> The South Texas Onion Committee set a guideline that its sweet onions should be less than 4.5 µmoles/ml.