It’s still a minor variety compared to plantings of other University of California-developed strawberries, but after flying under the radar in recent seasons, the portola variety is seeing a spurt of grower interest.

Trials done three years ago showed portola offered at least double the yield of other varieties planted in spring and summer in Santa Maria and Oxnard, Calif.

“I don’t know why people didn’t pay attention earlier,” said Doug Shaw, professor in the plant sciences department at the University of California-Davis.

“They didn’t have a cultivar in the past that would be tremendously productive in that system, and now they do. Before yield was a couple thousand crates per acre. With portola, it’s 4,000 to 5,000.

“Worldwide there’s a run on that cultivar, and no one has accurately estimated its increase over the last two to three years.”

For the May through July planting season, nurseries have been sold out of portola — even with a 40% down payment — for 18 months, Shaw said March 2.

One nursery’s business was up 2,000% over the year before.

Even so, plantings of the variety are modest in California’s central and southern growing regions.

“If the stock is available, we’re going to have about 1,200 acres this year of spring and summer plantings, half in Santa Maria and half in Oxnard,” Shaw said.

That could double in 2013, again pending availability.

Portola strawberries are similar in size to albion, the state’s most common variety with about 14,000 acres planted in 2011 from Santa Maria northward. Portola is shinier and lighter in color.

Both are day-neutral, or ever-bearing, varieties.

Portola’s flowering strength suits it to spring and summer plantings that bear much of their fruit from September to November.

Another UC-licensed variety, monterey, is making headway with about 1,300 acres planted.

“We could have sold double or triple that amount if the plants had been available,” Shaw said.

“It’s a day-neutral variety like san andreas, but more adapted to Santa Maria than Southern California. Fruit flavor is very nice. That’s why people were interested.”

High demand and short supply have been the rule lately on day-neutral strawberries.

“It’s not because nurseries aren’t growing the plants,” Shaw said.

“It’s because the market is changing for those varieties.”

New releases of the day-neutrals have lost much of their chilling sensitivity.

“My guess is day-neutral varieties will be featured in all early production systems, such as Southern California and Spain,” Shaw said.

“If I’d said 10 years ago that the largest single variety planted in Southern California would be san andreas, people would have said I’m crazy.”

About 4,600 acres of san andreas are planted, half each in Southern California and the Watsonville-Salinas area.

Historically, Southern California growers favored short-day or June-bearing varieties. Benicia, one of the newer university varieties, is an example.

“Most people with 80 or 100 acres want to buffer themselves, and having benicia and san andreas on different schedules does that,” Shaw said.

“Benicia was planted in the fall and it’s producing now. It’s the wild card. Things look good, but whether (plantings) stay the same, double or triple depends on what happens in the next six to eight weeks.”