ripping, fumigating, and leveling became nearly impossible.The cost and difficulties involved
were viewed as too great and trellis systems have been virtually abandoned within the stone fruit
industry.

Open Center High Density Systems
Kearney Perpendicular V
In 1982, University of California pomologists planted the first orchard of what would later
become known as the “Kearney Perpendicular V”system (DeJong et al., 1994).The system was
essentially a Tatura “V”without the trellis.Also, the spacing was not as close, the trees were
planted 6.5 x 18 feet.This planting compared the Kearney “V”with the open vase, parallel “V”
and central leader systems (Table 2).The system proved to have merit, and many orchards were
planted.Since then, many different spacings were tried, but the best seems to be about 6 feet
apart within the row and 16 feet apart between the row.

Table 2.Cumulative fruit yields in tons per acre for four peach, nectarine and plum training
systems for the first 10 years after planting (after DeJong et al., 1991a).

Flavorcrest
Peach

Royal Giant
Nectarine

System

Simka Plum

Central Leader
6.5’x18'
372 trees per acre

88.4

145.9

90.5

Kearney V
6.5’x18'
372 trees per acre

110.1

186.4

88.3

Parallel V
10’x18'
242 trees per acre

96.1

148.9

80.3

Open Vase
20’x18'
121 trees per acre

107.4

169.5

82.4

Quad V
In the late 1980s growers became concerned with the high initial planting costs of the Kearney V
System.In an effort to reduce tree costs, but at the same time increase early production, several
growers in the Dinuba/Traver area of Tulare County began experimenting with very close open
vase orchards in which trees were planted 10 to 12 feet apart down the row.These had very high
yields during the first 4 or 5 years of orchard life but, as the trees matured and grew together,
they began to have shade problems, causing yields to drop.Several of these orchards were
eventually modified by sawing out scaffolds oriented parallel with the row and leaving scaffolds
protruding into the alleyways.The rows had a rough “V” shape with an open center.

Shortly thereafter in 1990, an orchard was planted at the Kearney Agricultural Center comparing
the Kearney V and a variation of these modified close-spaced open vase orchards (Table 3).
From these orchards came what is now known as the “Double V”or “Quad V”system.Typical
tree spacings in these orchards are 9 to 10 feetbetween trees in a row, with row widths of 16 to
20 feet.Trees are pruned so that there are four leaders growing out into the alleyways.These
leaders support only fruiting wood and are not allowed to branch.Trees are essentially
structured and treated like a double Kearney V.Yields have proven comparable to the
Kearney V, but at a reduced establishment cost.

Table 3.Systems yield summary of the Kearney V and Quad V trial at the Kearney Agricultural
Center; yields in tons per acre (after Day et al., 1993).

Variety/systemz

1991

1992

1993

Total

Mayglo
Kearney V

1.06

5.36

7.25

13.67

Mayglo
Quad V

0.37

5.65

7.53

13.55

Sparkling May
Kearney V

0.72

5.76

8.87

15.35

Sparkling May
Quad V

0.376.7810.2217.38
zKearney V planted at 6’x18' for a density of 403 trees per acre; Quad V planted at 9’x18' for a
density of 269 trees per acre.

Other Considerations for HighDensity Systems
Both the Kearney V and Quad V systems combine advantages of the open center system with
those of other high-density systems.Because the center of the tree is kept open, light can
penetrate through the canopy during peak sunlight hours.An area is kept open between trees to
allow lateral sunlight penetration as well.Because of increased tree densities, full yield is
reached more quickly than with standard density systems.

Another quality of both the Kearney V and the Quad V is that every tree is nearly identical in
shape.Such uniformity makes it easier to prune and thin the trees.For example, if 300 fruit are
normally desired at harvest on a Kearney V, and if 3 fruit are normally left per fruiting shoot,
then the tree should be pruned so that 100 shoots are left—50 on each side.Double-checking
can be performed at pruning by counting the number of shoots and at thinning by the number of
fruit on each shoot.In this way, worker performance can be evaluated very quickly.

Despite the performance of the Kearney V and Quad V, many Californians have been reluctant to
embrace high density systems.This is primarily due to the expense related to planting.Current
tree prices are about $5 per tree with breeder royalty payments of $2 to $3 per tree as well.At $8

per tree, a high density planting could cost as much as $3500 for trees alone.The more popular
open vase system would cost about $1200. With California’s long growing season and excessive
vigor, the yield advantages of high density systems last only 1 to 3 years.Depending on the
other economics involved, this may not be enough to justify such an additional planting cost.
Consequently, few Kearney V systems are currently being planted in California.Because of tree
cost, most growers favoring high-density systems have switched over to the Quad V.

MinimalPruningof Open Vase Trees
In 1989, Day and Johnson (1997) began studying the effect of pruning severity on peaches and
nectarines.The experiment was expanded in 1992 to a newly planted block of Fairtime peaches
planted at an 18 x 18 foot spacing.The experiment (Table 4) had the following treatments:

1.

HH—trees pruned heavily at the end of the first and second growing seasons (normal for the
industry).
HM—trees pruned heavily at the end of the first season and moderately at the end of the
second.
LM—trees pruned very lightly at the end of the first season and moderately at the end of the
second
LL—trees pruned very lightly at the end of the first and second growing seasons.

2.

3.

4.

By the end of the third growing season, all trees had reached full height and were pruned the
same way thereafter.

Table4.Summary of Fairtime minimal pruning trial; trees planted in 1992 and trees first
cropped in 1994 (after Day and Johnson, 1997).

Total yield
1992 to 1997
(kg/tree)

Average fruit
size, 1992 to
1997 (g/fruit)

Trunk cross-
sectional area
1997

Scaffold cross-
sectional area
1997

Treatmentz

HH
HM
LM
LL

435ay
604b
619bc
687c

253a
237b
253a
226b

256a
254a
270a
303b

27a
30a
27a
30a

zSee numbers 1 to 4 above.
yWithin columns, values followed by the same letter are not significantly different.

The minimal pruning vastly outperformed the other systems and reached full production in the
third growing season (Table 4).There were no negative effects from the minimal pruning
system.Since this trial, numerous growers throughout the state have adopted this system.

MinimalPruning and Branch Bending of Plums
Minimal pruning studies were also performed on plums beginning in the late 1980s.From these
studies, a system has been developed which uses metal clips driven into the ground as anchors so
that limbs can be tied into the exact orientation desired.This pruning system has allowed plum
trees planted on an 18 x 18 foot spacing to reach full production in the fourth growing season.It
is important not to bend the branches below 50 degrees above horizontal so that the dominance
of the terminal growing point is maintained.