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MECHANIZED HEDGING
close-planted WALNUT
D. E. RAMOS * G . S. SIBBETT
been to set trees 40 to 60 ft apart (12 to together into a solid canopy and the
These two experiments indicate that once 27 trees per acre), allowing enough space other where they had not.
walnut orchards become crowded, hedging to fully develop the eventual large tree This experiment, conducted in Tulare
to allow light between trees is not effective and avoid crowding. Interest in closer County, compares the effects of hedging
in alleviating the condition. A substantial spacings occurred when two varieties heavily canopied walnut trees with de-
loss in production occurs initially and, al- were interset and the grower was unsure, tailed hand pruning, and no pruning, on
at planting, which one would eventually nut production and quality. Mature
though new growth develops in response t o
be kept. Payne walnuts, 13 years old planted 35
the hedging, it does not result in increased With the development of new varieties by 35 ft offset (25 ft between trees),
production, or in the’ restoration of lower which are compact in growth habit and which had been heavily canopied for
fruit wood. Hedging, however, may prove to highly fruitful on lateral buds, closer tree four years (see photo) were selected for
be a valuable tool in maintaining tree size spacing (20-30 ft apart) has become the test. Extensive shading and crowding
and production in orchards where the trees common practice to increase production had resulted in extensive loss of lower
fruit wood and production that had sta-
have not yet grown together. Work needs t o while the orchard is young. Yields per
tree are similar at all spacings early in bilized at an undesirable level. The plant-
be done to evaluate the effect of repeated the orchard’s life, thus, per-acre yields ing is in permanent border type culture
hedging where it is started before tree increase proportionately to the number and hedging was performed in one direc-
crowding has developed. of trees per acre. tion.
Close plantings are established with Mechanical hedger
the intention of systematic removal of
The hedger was a dual 22-ft, vertical
R ECOMMENDED SPACING for walnut
trees has changed during the past
twenty years. The common practice had
alternate trees as the orchards become
crowded. The size of the “temporary”
trees should be gradually reduced over
boom machine using seven circular saws
per boom (see photo). It was adjusted to
several years by progressive limb removal cut a 7-ft width at the top of the boom
to avoid a substantial production loss (22 ft high) and 4 ft at the bottom
when the trees are removed. However, Overhanging branches not cut by the
growers with good production are reluc- hedger were removed by hand. Hedging
tant to perform the necessary pruning was first done during the 1971-72 dor-
and ultimate removal of temporary trees. mant season and repeated in the two
The orchards, thus, become crowded, subsequent years.
shading develops and production stabi- Six, one-acre plot replications (42
lizes or declines. When orchards reach 10 trees) of the following treatments were
to 15 years of age, declining production established: ( 1 ) hedging both sides of
becomes apparent as lower fruit wood tree row each year; (2) hedging alternate
becomes shaded and nuts are borne only sides of tree row each year; (3) hand
in the tops of trees. This is the situation pruning: 20 to 25 moderate (1- to 2-
which appears to be developing in many inch) cuts per tree; and ( 4 ) no pruning.
present day walnut plantings. Yields were obtained for a three-year a
The question has arisen as to the feasi- period, and Diamond Walnut Growers,
bility of substituting mechanized tree Inc., made the quality analyses.
hedging as an alternative to tree removal Annual and total production for each
to maintain high production of close- treatment is presented in the table. In the
planted orchards. Hopefully, this would first year of the test, hedged treatments
allow light to penetrate between tree rows produced significantly (P = < .01) fewer
and increase nut production. This report walnuts than hand pruned. This result
describes the results obtained from hedg- was to be expected because of the large
Sickle bar hedging machine used in Tehama ing walnut orchards in two different situ- amount of wood initially removed by the
County trial. ations, one where the trees had grown hedger (see photo). In succeeding years,
10 CALIFORNIA AGRICULTURE, JANUARY, 1975
of trees, were compared with hand prun-
ing, and no pruning, in a trial near Vina,
Tehama County. The walnut trees (10-
year-old Vinas planted 25 by 25 ft
square) were just beginning to touch and
nuts were being produced throughout the
tree when the pruning was performed in
the 1971-72 dormant period.
The hedger was a 14-ft, double-bladed
sickle bar attached to a boom mounted
on a wheel tractor (photo). The cutter
bar was positioned at about a 30’ angle
J. W. OSGOOD E. RONCORONI
from vertical. No pruning was done be-
low 8 to 10 ft from ground level nor in
the top center portion of the tree.
Harvest data was obtained only in
no significant difference in production
1972, the first season after the differential
was obtained between any of the treat-
pruning treatments. There were four r e p
ments although hedging produced con-
lications (40 trees each) of each treat-
sistently fewer walnuts than hand- or non-
ment. No significant difference in yield
pruning treatments. Nut quality was not
was obtained between any of the treat-
affected by any treatment in any year of
ments. Nut quality was also unaffected.
the experiment.
The machine pruning produced about
Hedging did not alleviate shading.
as much new growth ( 2 to 3 ft) from
After cutting back old fruiting wood by
pruned limbs as did the hand pruning.
hedging, substantial vigorous new growth
In both cases, the pruning consisted pri-
developed and the orchard was again
marily of heading-back previous year’s
canopied by July of that growing season. growth on the periphery of the tree. Un-
Rehedging both sides o the row the fol-
f pruned limbs, in most cases, grew very
lowing dormant season, as in treatment little regardless of treatment. Mechanical
No. 1, removed a very small amount of Walnut hedging machine used in these Tulare County trial
hedging did not appear to increase featured seven circular saw blades mounted vertically on twi
wood and did not appreciably improve crowding between trees. By the end of booms, allowing trimming from either side of the row withou
light conditions in the lower portion of the summer, trees left unpruned were the turning around.
the trees. Allowing new growth to remain most crowded, and production would be
the following year (treatment No. 2 ) did expected to gradually decline if crowd- ANNUAL AND TOTAL DRY YIELD OF PAYNE WALNUTS AS AFFECTEl
BY PRUNING TREATMENT IN HEAVILY CANOPIED ORCHARD
not increase production because the one- ing was allowed to continue. IN TULARE COUNTY
year-old wood did not seem to attain the
DRY TONS/ACRE
high degree of lateral bud fruitfulness D. E. Ramos is Extension Pornolog&,
characteristic of the variety. Moderate University of California, Davis. C. S. Sib- 1972 1973 1974 TOTAL AVG/YI
hand pruning in this test did not improve bett is Farm Advisor, T&re County. J . Hedging both sides
light penetration, or production, as com- W . Usgood is Farm Advisor, Tehama of row .55 1.54 1.06 3.15 1.05
Hedging alternate
pared with the non-pruned treatment. County. E. Roworoni is Staff Research sides .69 1.67 .94 3.30 1.10
Two hedging treatments, both sides Associate, University of California, Hand pruning 1.04 1.70 1.10 3.91 1.30
NO pruning .84 1.80 1.27 3.84 1.28
of trees in one direction vs. all four sides Davis.
Walnut hedging, before (left) and after (right), photos at the Robert’s-Gregory Ranch, Tulare County. The trees were 13 years old and about 30 ft high.
CALIFORNIA AGRICULTURE, JANUARY, 1975 11
