Ivanhoe, A New Early Walnut
July 1, 2010 
While Ivanhoe should be a great fit for many growers, those in particularly wet areas may want to avoid it, as it tends to be susceptible to blight.
University of California (UC) researchers are excited about a new walnut cultivar, “Ivanhoe,” that’s being released this year. Not only does Ivanhoe produce the desirable light-colored kernels for which the popular Chandler variety is known, but it is harvested a month before Chandler. With Chandler, the state’s dominant variety, being a relatively late harvester, growers have had a logistics problem, explains Chuck Leslie, who heads up the walnut breeding program at UC-Davis.
Growers have tried to fill that early harvest window in the past with a number of varieties, such as Serr, but haven’t gotten the traits they desired. With Ivanhoe, they should get high yields and light-colored kernels, says Leslie.
“We’re hoping this will fill that niche,” he says, “and at the same time maintain better color quality.”
Bloom Boon
Ivanhoe has a harvest date similar to Serr, as well as Payne, and those two varieties, as well as Ashley, should make excellent pollenizers. The reason they should work so well is that Ivanhoe has reversed female-to-male bloom. In most standard varieties, Leslie explains, the male flowers bloom first, then the female flowers. But in Ivanhoe, as in one of its parent cultivars, Chico, the female flowers bloom first. The other parent is a numbered variety, UC67-13, and Ivanhoe gets its name from a town in the southern San Joaquin Valley, where it should prosper (see “Not For Everybody” below).
The bloom advantage is that Ivanhoe’s female flowers will be open at the very same time it can get pollen from the Serr because Serr’s males open first.
“And then as Ivanhoe’s males shed pollen the Serr’s females will be open,” he says “So Serr, Payne, and Ashley will all serve as good pollen sources for Ivanhoe.”
Leslie says Chico was chosen as one of the parents to obtain large yields. Though they don’t have a lot of measured yields, so far Ivanhoe looks good. It sets a good heavy crop. The one concern he has regarding yield is that the nut sizes are not overly large, with kernels averaging 7.7 grams and comprising 57% of the nut weight.
“As they mature, older trees’ nut size can decline, so that is a concern,” he says. “We’ll just have to see how that plays out as the trees mature.”
Walnut nurseries have been notified of the release of Ivanhoe, which can be purchased from any licensed commercial nursery.
Not For Everybody
While the new Ivanhoe cultivar should be a great fit for many walnut growers, it is intended only for those growers in the state’s drier regions, emphasizes both Leslie and UC Farm Advisor Emeritus Bill Olson of Butte County. Olson has collected samples for the past five years from a trial in Chico, which is located toward the north end of the state’s growing regions, and has found Ivanhoe to be extremely susceptible to walnut blight.
In fact, for the past two springs, Ivanhoe was the only variety out of a total of 58 selections that showed any blight in the trial. It’s definitely a risky proposition for growers in the northern parts of the state that get a lot more rain and where blight is far more of a concern, Olson concludes.
“It’s a big problem in our area, especially in a year like this with a wet spring,” he says. “But from Modesto-south, it will probably be an excellent fit.”
On the bright side, Olson confirmed Leslie’s findings of excellent nut quality, with near 90% light-colored kernels. In addition, there is one other early cultivar which is not named yet that will be out in the near future. While not as early as Ivanhoe — it’s about two weeks later — it’s a much better fit for north-state growers, says Olson.
“There are other selections in the mill,” he says, advising growers in the region to be patient. “It’s not like, ‘Oh gee, this is my last hope.'”
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