Nine Palms Ranch Trial, 2007

Lead: Bracey Tiede and Joan Kendig

Summary

Sweet onions can be grown easily in Santa Clara County, given the proper care and timing. Super Star was rated the highest with Candy and White Sweet Spanish close behind.

Overview

We trialed eight varieties of sweet onions to determine the best tasting sweet onion. Onions have differing day-length requirements to form bulbs. Long day onions require a longer period of daylight to form bulbs. This happens north of our latitude. The San Francisco Bay area is on the latitude between long day and short day types so our trial included both of these as well as day neutral types (which will bulb without regard to day length). The plants were grown from seed. The varieties trialed were Ailsa Craig Exhibition (long), Redwing (long), Tropea Rossa Tonda (long), Walla Walla (long), White Sweet Spanish (long), Candy (neutral), Super Star (neutral) and Yellow Granex/Vidalia (short). The onions were red, white and yellow in color.

Team members

Bracey Tiede was the lead on the project with valuable assistance from Joan Kendig and Faith Lindsay. Onion seeders, weeders, waterers, tasting prep team members and tasters were drawn from Nine Palms Ranch regulars as well as other Master Gardeners. Many thanks to them all.

Harvested sweet onions in June

Soil preparation

Prior to planting in mid-November, the soil in the 35-foot raised bed was amended with horse compost from Garrod Farms of Saratoga and a bag of added minerals we had left from an organic product donation. About 4 inches of compost was dug into the bed.

Seeding and transplanting

The onions were seeded on September 18 and 22, 2006, in 16-inch square flats in SuperSoil potting soil with a small amount of added pelletted fertilizer. They were placed in the shade house and misted several times a day. Of the eight varieties, all but one of them produced a minimum of 35 successful seedlings.

On November 14, 2006, the seedlings were planted in a grid pattern in the divided raised bed. Each variety had a 4-foot x 3-foot section and seedlings were on 6-inch centers from plant to plant. The plants were then covered with thin row cover that was raised above the plants with boards and anchored on the sides with pipes and bricks. This was done to prevent disruption by local squirrels, other mammals and birds.

Watering

The onions were watered as needed by hand through the winter. The soil moisture level was tracked weekly using a moisture meter in multiple places in the bed. The row cover was removed in February, 2007, as the plants pushed up against it. Watering was stopped on May 1.

Fertilization and Pesticides

Essential 101 fertilizer was applied on March 27, 2007. This liquid product is N1-P0-K1 and is advertised to be a plant food/soil conditioner. I could find no further information about this product. It was left over from an organic product donation. No pesticides were used.

Harvesting and observations

Onions will be successful if they reach a width of narrower than a pencil in January. Fortunately, our onions kept to this standard and grew slowly through the spring. Two bulbs of White Sweet Spanish formed flowers and were pulled on April 24, 2007. On May 22, 2007, Super Star had two bulbs with flowers forming which were pulled. The Vidalias (short day onions) were pulled two weeks before the rest.

Super Star pulled

Sweet onion variety	Seed source	Day length	Color	Count	Total weight	Average weight	Harvest dates
Ailsa Craig Exhibition	Pinetree	Long	White	33	11 lb 8 oz	5.5 oz	June 5
Candy	Park Seed	Neutral	White	29	18 lb 1 oz	10 oz	June 1, June 4, June 5
Redwing	Pinetree	Long	Red	28	11 lb 5 oz	6.5 oz	June 5
Super Star	Pinetree	Neutral	White	33	22 lb 15 oz	11 oz	May 22, June 5
Tropea Rossa Tonda	Franchi Sementi	Long	Red	32	9 lb 5 oz	4.6 oz	June 5
Walla Walla	Pinetree	Long	White	25	8 lb 14 oz	5.7 oz	June 5
White Sweet Spanish	Pinetree	Long	White	23	11 lb 10 oz	8 oz	April 24, June 5
Yellow Granex/Vidalia	Park Seed	Short	Yellow	28	26 lb 13 oz	15.3 oz	May 22, May 25

Vidalia was picked early and were the largest of the onions. One Vidalia and one Super Star each weighed 1.5 lbs. Candy and Ailsa Craig each had one of 5” diameter. If we had left the onions to grow longer, they may have grown larger. Our maximum day length is about 14-1/2 hours in mid June. Long day onions really need 16 hours of daylight for full development.

Initially 35 of each variety were planted. The missing number of onions is a mystery. Critters of unknown origin presumably got them.

Tastings

Tastings were handled in two ways. Raw tastings were done at Nine Palms and the June Advanced Training. One roasted onion test was done at Nine Palms. Other onions went home with Nine Palms tasters for consumption either raw or cooked at home. All the onions were sweet when initially tasted raw but most had an after-'bite'. Cooking them brought out the sweetness even more. Super Star was the big winner on taste, crispness and productivity eaten raw. Ailsa Craig won the roasted category for sweetness and flavor.

Tasting onions

Conclusion

Sweet onions can be grown easily in Santa Clara County, given the proper care and timing. Super Star was the super star of the trial. It was large, white, crispy, sweet and productive, making it the favorite. Candy and White Sweet Spanish were close behind, though White Sweet Spanish only produced half as much by weight as Super Star. Yellow Granex/Vidalia was the most productive but not rated as highly for sweet flavor.