Walnut bloom for San Joaquin County grower Chris Locke started with Serrs, Vinas, Hartleys, Howards, and Tulares, and will be followed by Chandlers, the last to bloom in late April.
“Right now, the trees are in good condition,” says Locke, who has 580 acres of walnuts near Lockeford, Calif., on land next to the Mokelumne River that his great great-grandfather began farming in 1850. His father planted the Serrs in the late 1960s and early 1970s. Next to go in were the Vinas, Chandlers, Hartleys and Howards. The Tulare blocks date back 11 years.
Locke’s orchards also include a few acres of Hartleys and Franquettes, which his grandfather planted 90 years ago. Located along roadways, they stand about 50 feet apart, with other varieties interspersed between them.
“It’s a sentimental thing,” Locke says. “I like to keep these old trees around to remind me of our farm’s heritage and deep, alluvial soils.”
These trees yield about 1,500 pounds of nuts each season. “Those trees are a little hard to shake,” he explains. “They were grafted really high and the trunks are too thick to shake. So we have go up on the limbs and shake what we can, then wait for the winds to shake more nuts off the trees.”
The tree spacings inhis orchards range from 28 x 30 feet (52 trees per acre) for the most vigorously-growing varieties, Chandler and Serr, to 16 x 24 feet (100 trees) per acre for Howard, the smallest trees. Because the trees grow well in this flood plain location, Locke wants to keep trees far enough apart to minimize shading, which can reduce nut yields and make control of the husk fly, which prefers dark, shady, humid areas, more difficult.
To control codling moth, his first insect threat of the season, he has relied on pheromone-emitting puffers, rather than insecticides. “The puffers and pheromone have been pretty successful for us,” he says. “They don’t provide 100 percent control, but they allow us to manage codling moth and prevent any serious damage from the insects.”
This summer he’ll begin spraying for walnut husk fly. He’d like to use a material that won’t harm the Trioxys pallidus wasp, which helps control walnut aphids.
Mites haven’t been a problem for Locke, but aphids can require control from time to time. He’ll begin monitoring for them probably in late June, treating as required.
Like other growers this past dry winter, Locke irrigated his orchards in December and January. In addition to replenishing the soil profile, this helped sustain cover crops, which include annuals such as triticale and mustard, and legumes like mustard pea, bell bean and vetch.
He’s been planting cover crops on his orchard floors since the mid-1980s. “I’m a firm believer in cover crops,” he says. “They build organic matter levels in the soil and the legumes fix nitrogen. Also, the cover crop improves soil drainage. If we get rain at harvest, that allows us to get back into the fields sooner. ”
He keeps vegetation mowed during the growing season, and seeds the cover crop with a no-till drill in the fall. “Ever since we stopped disking about 15 years ago, the soil and trees are healthier and there’s less dust during harvest,” he says.