Following a period of delayed May growth due to prolonged wet spring weather, the third-leaf walnut trees in Keith Larrabee’s Glenn County orchards began rebounding in mid-June, and within a month were happy and thriving once again.
“Now, they look excellent and are growing very nicely,” he says. His young walnut trees are replacing prune orchards he in planted in 1991. His deep, well-drained Class I and II silty clay loam soils are well-suited for walnuts.
Based at Chico, Calif., Larrabee Farms also grows rice, prunes and pecans in both Glenn and Butte counties. Larrabee, who is a director of the California Pecan Growers Association, started growing pecans nine years ago.
“I think walnuts have a more promising future than some of the other alternatives in this area, like prunes,” he says. “The market for tree nuts, in general, looks positive as demand for all nuts continues to increase.”
Chandler is his primary walnut variety, along with a field of Howards. He planted the Chandlers on a 28-foot row spacing, placing the trees 26 feet apart within the rows. The trees in every other row are offset 13-feet within each row from the trees in the adjacent row, creating an offset pattern. This provides a little more room than planting the trees in a square pattern with the same between-tree distances.
The smaller Howards are planted in a similarly staggered manner, creating an offset pattern, with the trees placed 25 feet apart between rows and 18 feet down the rows.
Before he began replacing prunes with walnuts, Larrabee sought the advice of experienced growers — and he still does.
“When I see things happening in my orchard that I have questions about, I talk to those who have been in the business longer than I have, to glean information on what to do and what not to do. Whenever you plant a new crop, you learn a lot the first year, and you build on that in the following years.”
Larrabee says there’s definitely a difference between growing walnuts and pecans. He discovered one difference the year he planted his first walnut trees: “They’re very temperamental when it comes to water. They like to drink, but they don’t like to have wet feet. With other tree crops, you can pour water to them and they continue to perform.”
He’s taken that lesson to heart in the way he manages his irrigations with solid set sprinklers. He gives the walnut trees less water each irrigation, but applies it more frequently.
“I don’t want to over-saturate the soil, especially during the first two years,” Larrabee says. “When the trees are really young and coming out, I give them only half an inch of water each time, but they get it every week or two. As the heat comes on in the summer and the trees are pushing out nicely, I may increase the application rate, but the frequency stays the same. As the trees get older, I increase the amount of water applied each time.”
This season, once the weather started getting hot in July, he’s been watering his trees every one or two weeks, applying anywhere from ½ to 1½ inches of water with each irrigation, depending on weather and tree conditions.
Larrabee takes leaf samples every year in July to check nutrient levels. Because of his rich soils, there was no need to apply any fertilizers until this spring, when he spread a pound of Triple 15 around the base of each tree just prior to an irrigation. Results of the leaf analysis done this month indicate the trees are doing well nutritionally.
He limits herbicide use to controlling a broad spectrum of weeds, including lambsquarter, pigweed, johnsongrass and watergrass. To avoid possible damage to young trees from soil-applied pre-emergence herbicides, he treated the tree rows with paraquat (Gramoxone) or glufosinate-ammoniumduring the first two years. This year, he switched to applying low rates of glyphosate (Roundup) or 2,4-D in the tree strips. He mows the weeds in the middles.
“You have to be really on top of weeds to control them with contact products,or they can get of hand quickly,” he says. “I go in a little earlier than I normally would when using soil-applied materials to prevent any escapes. But, this approach is working well.”
Larrabee continues to monitor his walnut orchards for diseases, as well as insects, mites and other pests. So far, he’s had no outbreaks. To provide hosts for pests, he keeps a good cover crop of native plants — clovers in the spring, which give way to grasses in the summer — in the row middles.
Other than continuing irrigation, mowing weeds and watching for any pest threats, Larrabee’s main concern for the rest of the season is keeping the walnut trees as healthy and vibrant as possible.
“We want to have good solid trees going into winter,” he says. “We’ll use leaf analysis to make sure we’re meeting the trees’ nutrient needs, so next spring when the trees start pushing out they’ll be ready to roll.”