Caster, a biologist, is evaluating nearly a dozen varieties of blueberries at a six-acre demonstration site near the Watsonville headquarters of the fresh-fruit shipper that also handles strawberries, raspberries, and blackberries.
Blueberries are also adaptable to frozen, juice, or dehydrated utilization, and as ingredients in processed foods, but at the moment Caster is mainly interested in developing new varieties for the fresh market.
Several public varieties are being grown in California, and state acreage is estimated at as much as 700 acres and increasing. California producers seek markets during May when national volume is low and prices are high.
Caster said Driscoll is looking for grower-partners who can produce top-quality fruit. "In turn, we offer the best in outlets for wholesale and retail, the food service sector, and exports. We ship to the best customers and offer our growers larger volume and a strong brand name."
Growers having experience with tree and vine crops and other berries might be more likely interested in producing the crop, but vegetable growers certainly are not excluded, he said. "Blueberries may require some more attention than other crops, but they are not particularly difficult."
However, they do require soil with a low pH and adequate organic matter, and good drainage. Some varieties are more drought-tolerant than others, and irrigation practices have to be adjusted accordingly.
Yields may reach 15 tons per acre in the Pacific Northwest, but in coastal California typical varieties bear lightly in the second or third year and may reach five- to eight-ton yields in the fifth year.
USDA has been working for the past several years on breeding of hybrid blueberries. Work by USDA in Maryland and Mississippi and by the University of Florida paved the way for varieties suited to California conditions.
Cultivated varieties are known as high-bush types, reaching a height of six to ten feet, while wild species, or low-bush, range to 10 inches high.
Traditional cultivated blueberries are known as northern high-bush types and have a high chilling requirement during the winter as do many tree fruit crops. The chilling requirement prevented northern high-bush cultivation in the warmer, more southerly latitudes.
But in the southern high-bush blueberry cultivars the chilling requirement was reduced and they opened new locations for production. "That’s really at the heart of what’s going on in California with blueberries," said Caster.
The southern high-bush plant has ancestry in the northern high-bush plants hybridized to a blueberry species native to the southeast.
Although the crop is being grown on the California coast, it tends to occupy ground for 10 to 50 years, a much longer commitment of land than raspberries, strawberries or vegetables.
Caster says that and high land values could limit blueberry acceptance on the coast, and he sees expansion more likely in the San Joaquin Valley, from Stockton to Fresno, due to cheaper land and the early maturity for a May market window, when supplies are low and prices are high.
While they might be grown farther north in California, Caster said the season would be closer to that of Oregon without the marketing advantage of areas to the south.
University of California researchers at Parlier in Fresno County report that blueberries mature there from mid-March to mid-May. Yields there tend to be more concentrated during a shorter period than the coast. Some low-chilling, southern high-bush varieties fruit again in the fall.
They also report some hazard to earlier fruiting varieties from spring frosts aborting flowers and delaying production.
Blueberries are grown in North America during the spring and summer and in South America during the fall and winter. The crop’s ability to be cold-stored allows a year-round supply to maintain consumer interest.
According to Mark Gaskell, farm advisor for Santa Barbara County, wholesale blueberry average prices at the Los Angles Terminal Market during 1998 to 2000 were about $20 per flat (12, six-ounce baskets) most of the year.
Price peaks came during mid-May at $50 and again in early December at $40. A low of just under $10 occurred in mid-August.
Blueberries are planted 1,200 to 1,500 per acre, spacing is three to four feet between plants and nine to 12 feet between rows. Trellising may or may not be used but does support heavy-yielding bushes and drip irrigation lines.
3 to 5 pickings
Typical harvesting for the fresh market — three to five times during the ripening period — is by hand. In the northwest, Caster says, mechanical harvesting is used for the final crop after hand picking of the earlier fruit.
Bushes are pruned by some growers each year and every other year by others, and Caster said the object is to remove unthrifty canes. At maturity, one to three oldest canes are removed each year to encourage new growth and promote air circulation.
"In California, blueberries seem, thus far, to be remarkably free of diseases. We don’t see the root and berry rots they are subject to in wetter parts of other regions," he said, adding that he is not aware of any problems from nematodes or other soil-borne pests at the company test site.
The Driscoll test site, however, is draped with netting to keep out birds. "A smaller field especially benefits from netting, and if the field is 15 to 50 acres the bird damage would be proportionately less. That might be acceptable, but we are taking yield data from these plots."
He said he has no knowledge of the crop being susceptible to the glassywinged sharpshooter or Pierce’s disease. Weevils and aphids, and, in other areas, moth pests, do go to the blueberries.
"Blueberries," said Caster, "have an optimistic future now in our agriculture that has a lot of troubles. There is a good chance they can become an important crop in California. I would have to caution growers that blueberries can’t be a pot of gold at the end of the rainbow indefinitely.
"As more acres go in and production volume picks up, just as in any other crop, the law of supply and demand will have to be strictly obeyed."