West Coast Nut September 2019

North Valley Nut Conference see page 55
January 21, 2020 | 7:00AM - 1:00PM | Orland, CA
It can be particularly damaging for young trees when
temperatures drop to 28 degrees F or below before they’ve
experienced a few nights near 32 degrees F to become
acclimated.
Trees can be managed for cold hardiness by:
•Stop nitrogen fertilizer applications after September
first to avoid new growth.
•Stop irrigation in mid-September until terminal vegetative
bud set.
•Once the terminal vegetative bud has set by mid- to
late-October, another irrigation can take place if there
has been no rain. On both mature and young trees this
will moisten the soil and prevent premature defoliation
without pushing new growth.
•Use protective white latex paint on the trunks.
•Delay pruning until March after the threat of frost
is past.
New, vigorous growth on young trees is
especially sensitive to frost injury. Photo
courtesy of Janine Hasey.
vegetation bud is set water can be applied without
resuming growth.
Higher Elevations
Rachel Elkins, UCCE pomology farm advisor and
county director in Lake County, said, her growers typically
get a certain amount of late fall or winter injury
every year because they’re at a higher elevation.
Continued on Page 46
Mature Trees
Luke Milliron, UCCE orchard systems advisor for
Butte, Glenn and Tehama counties said, the concern for
fall freeze damage has historically been young walnuts,
but mature trees can be susceptible, too, under the right
circumstances.
Previously young trees, in particular, were associated
with autumn early freeze events, but in November 2018
young and mature trees were severely impacted with freeze
damage in early November, Milliron said.
Whether mature or young trees, the advice remains the
same, with increased caution for young trees, Milliron said.
“With young trees you don’t want all this new tender
growth that gets freeze damage, so you start that process
of not heading into autumn with a bunch of brand new
growth,” Milliron said.
Water Management
Water management is a critical step to encouraging
terminal bud set. Growers are advised to avoid irrigating
in September until growth at the tips of the branches has
stopped. Stop water until there is no new growth and
red leaves, but not until the leaves yellow and defoliation
occurs. Resume irrigation in October if there is no rainfall
to ensure the soil is moist before a November freeze event.
“Withholding irrigation beginning in roughly mid-September
until you see that a terminal vegetative bud has
formed on the trunk,” Milliron said, is the best protection.
Milliron reminds growers that once the terminal
September 2019
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