Pete Jelavich has been growing walnuts for more than 20 years and calls this year’s harvest one for the books.

“It’s been the most unusual harvest I’ve gone through,” says the Yuba City, Calif., producer. “The harvest started two weeks later than usual and the rains began two weeks earlier than normal.”

That doesn’t include problems earlier in the year caused by an unseasonably cool, wet spring, which disrupted tree bloom and nut set, and slowed crop development. “It’s been a challenging year in terms of both production and quality,” Jelavich says.

His mid-size walnut operation includes orchards in Sutter and Yuba counties. Normally, he starts harvesting his crop during the first week of September. This year Jelavich began on Sept. 20 with his earliest varieties — Serrs, Vinas and Tehamas. Then he moved on to his later-maturing Howards and Hartleys before finishing with Tulares and Chandlers. He harvested the last of his 2011 crop on Nov. 1. That was two days before another rain shower arrived.  “I’ve never finished this late before,” he says.

Rains in the first part of October led to a 10-day stretch when harvest operations bogged down. “Everyone wanted to pick the nuts, including the green ones, at the same time to beat any more rain,” Jelavich explains. “Normally, hullers can dry walnuts in about 15 to 20 hours. But this year, it was taking as long as 30 hours and more.” As a result, trucks were unable to unload their nuts. Until the processors could catch up, growers left their walnuts on the trees, biding their time as they waited for empty trailers to haul the nuts away.

The harvest also started and ran later than usual for Donald Norene, Rio Oso, Calif. He grows six varies of walnuts on 700 acres, also in Sutter and Yuba counties. This year, he began harvesting them on Sept. 15. That’s at least a week later than usual and three days later than last year’s start.

The delayed start prompted him and other growers to treat their trees with ethephon to shorten the harvest period. The plant growth regulator accelerates hull cracking and separation from the shell. This can advance walnut harvest by four to seven days. It can increase nut value by promoting lighter kernel color.