The length of the day plays a large role in the development of sweet onion bulbs, thus farmers in Hawaiʻi have historically been limited to growing only “short-day” onions, especially during the winter when days are shorter.
However, there are options for growing intermediate-day varieties in the summer months, and this potential opportunity drew more than 30 growers and community members to Extension’s recent field day at Poamoho Experiment Station.
“We initially evaluated 18 varieties classified as short-day types to confirm that if grown during the shorter winter months in Hawaiʻi, they would form marketable bulbs,” says Jensen Uyeda. “Six varieties showed to be very productive during the shorter months.”
Because sharing applied science with the public is a core mission of Extension, the Oʻahu County agents invited the public to Poamoho, where each participant was able to observe each variety in the field, as well as harvest varieties they were interested in tasting. The knowledge can help sweet onion producers make more informed decisions on which varieties will maximize their yields during the shorter days.
“It was great being able to physically show the community how the onions were grown and their potential in the field,” says Jensen. “Many times as researchers we show presentations and reports but when participants get a chance to pull a mature onion from the field, it gives a greater appreciation, which hopefully sparks more interest in producing this crop. We hope it will help increase the success of sweet onion production in Hawaiʻi, and lead to increased supply of local sweet onions in local markets.”
He adds that Extension continues to conduct research on sweet onions to identify new and more productive varieties, as well as best management practices to help commercial onion producers stay in production or even expand production.
“I expect to conduct this field trial again in the summer to see how the same varieties do during the longer days, and then develop a more comprehensive planting schedule for the whole year so that the industry can maximize their yields all year long,” he says. “We also expect to conduct shelf stability studies once we identify the more productive varieties. The storage capability without refrigeration of bulb onions make it a good crop from a food security standpoint.”