close to the timing of planting to prevent “glazing” of
the soil by the sun. If the holes are dug with an auger
or prior to the planting day, slice the sides of the whole
with a shovel to break any crust that may have formed.
When planting, the hole should be large enough to fit the
entire root system without bending or wrapping. Forcing
trees into planting holes causes “J-rooting” and increases
the chance of crown gall and tree loss. Plant the tree
high enough so that the nursery soil line is just above
the current soil line. Backfill the soil and compact gently
around the tree’s base to remove air pockets. Tank the
tree in with 4–5 gallons of water to help settle the soil.
Trees should be headed at 32”–36,” staked with the stake
placed 12” from the tree, and side branches pruned to
1/4”. Fertilizers should not be applied until there is 8–10
inches of new growth.
Planting may not always go as planned due to weather.
Hand planting crews have an easier time than machine
planting due to limited field access. If planting delays
occur, trees should be placed into cold storage at the
nursery as soon as possible to reduce the risk of leaf
out and weakened trees. Keep trees in cold storage until
ready to plant. Unless there is no other option, do not
take delivery of trees and store them in bins or plant them
in a temporary location at the farm. On delivery, check
tree roots to make sure they are healthy and living (should
be white in color). Trees planted late (e.g. mid-April)
should be painted white to reduce sun-burn risks.
Herbicides
This is a good time to apply any pre-emergent
herbicides. Orchard weeds need to be surveyed to
determine any specific challenges. The pre-emergent
product and burn-down partner selected should
provide control for the whole spectrum of weeds
within the orchard. If trying to manage summer
emerging grasses (i.e. goosegrass or junglerice), a
second, late spring-times pre-emergent application
could be considered. Most pre-emergent products
need to be “watered-in” with either an irrigation or
rainfall to have efficacy.
Delays in pre-emergent herbicide application from rain
can create a few issues. Rain events knock down debris
that can hinder the application or uniform incorporation
of herbicides. If not able to re-clean the berms, avoid
pre-emergent herbicides that are more tightly bound to
organic matter (e.g. Alion
®
, Prowl H2O
®
). Consistent rains
also limit field access which, in combination with warming
temperatures in the spring, increases weed germination
and rapid growth. Delayed applications of pre-emergent
materials will likely require tank mixing with burndown
herbicides and possibly even a separate, post-emergent
herbicide application. On very sandy soils, high rainfall
events may also move some pre-emergent herbicides into
the tree rootzone, which may impact plant performance if
the tree is active. Reduce rates in these situations.
The Final Thought
There is a good chance that this winter will be dryer
than average, and most certainly we will have less
rainfall than last year. A dryer winter typically means
warmer days, which will accelerate tree development,
increasing the risk of frost damage. Be wary of the
cold nights as below freezing temperatures should be
mitigated with frost management techniques. This could
include the application of irrigation water, management
of cover crop, or other mechanisms to increase heat
within the orchards.
David Doll, UCCE
Nut Crop Pomology
Farm Advisor,
Merced County
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