Quote:The primary advantage of central leader trees . . . is the reduction of labor.

HIGH DENSITY PEACH PRODUCTION IN ONTARIO

Neil W. Miles1, Rocco Guarnaccia2and Ken Slingerland3

1Associate Professor,2Research Technician, University of Guelph, Department of Plant
Agriculture, Horticultural Research Institute of Ontario Vineland Station, Ontario, Canada;
3Tender Fruit and Grape Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs,
Vineland Station, Ontario, Canada

Presented at the 42n dAnnual IDFTA Conference, February 20-24, 1999, Hamilton, Ontario,
Canada.

The Niagara region, the area between Lake Ontario and Lake Erie, in Ontario, Canada, produces
more than 85% of Canada’s peaches and nectarines.Other primary production areas include the
extreme southwestern section of Ontario (along the northwestern shore of Lake Erie and
southwest of Detroit, Michigan) and in British Columbia.In the Niagara region, peach and
nectarine production is limited to a narrow strip of land 2 to 10 km wide and 60 km long (1.2 to
6.2 miles wide and 37 miles long) between the south shore of Lake Ontario and the Niagara
escarpment, a bluff rising 100 to 200 m (325 to 650 ft) above the lake.

The unique microclimate formed between the lake and the escarpment is suitable for the
production of “tender fruits” such as peaches, nectarines, sweet and sour cherries, pears, plums
and apricots and grapes.Flower and vegetable greenhouses, nurseries and poultry farms also
flourish in this microclimate.To compete with these crops for the limited land base and to
produce the domestic supply for fresh and processing fruit, peaches and nectarines must be
productive and profitable.

The Ontario peach and nectarine industry is on the northern frontier for commercial production.
The Niagara tender fruit belt climate is characterized by harsh winters with the lowest recorded
minimum of -26.7ºC (-16ºF), short growing seasons (182 frost free days), and cool summers
with an average temperature for June, July and August of 20.2ºC (68ºF).Under these conditions,
tree growth and vigor is limited.Fruit production is consistent from year to year (1981 and 1994
were the only years in recent history when yields were significantly lower than average);
however, productivity in a given year is less than desirable (5.5 tons/acre provincial average).

The standard training systems in Ontario have been the open center and modified leader.To
improve the productivity and efficiency of Ontario orchards, many growers have been replacing
the standard open center and the modified leader training systems with central leader training
technology.In previous research, it was determined that better productivity could be obtained
from trellis trained central leader trees (Miles, 1992, 1998).This technology was modified to
freestanding central leader trees to eliminate trellis costs.

The primary advantage of central leader trees over the previous systems used is the reduction of
labor.More than two-thirds of the fruit is produced on the four major scaffolds that are oriented
close to the ground.Because tasks such as pruning, thinning and harvesting can be done without
ladders,fewer labor inputs are required.Orchard workers can easily learn the concepts of

training and pruning central leader peach trees.Other advantages include improved light
distribution and better spray distribution within the canopy.

The central leader peach tree system used in Ontario orchards is similar to the central leader
training system commonly used in apple orchards.The properly trained tree has four distinctive
parts:a strong central trunk, a vigorous apical bud, four major scaffolds arising from the lower
portion of the trunk, and numerous small branches along the upper portion of the trunk
(Figure 1).

Establishing a central leader orchard starts with initial training at planting time and continues
semiannually with spring pruning (bloom period) and summer pruning (coinciding with pit
hardening).In the first few years, four strong scaffold branches are established in the four
compass directions and spaced vertically 10 to 15 cm (4 to 6 inches) apart along the lower trunk.
The lowest branch should be directed into the prevailing wind and originate 50 to 76 cm (20 to
30 inches) above the soil.Pruning cuts direct the growth outwardly and encourage rebranching
and stiffening of the scaffold.A strong and vertical central trunk that terminates at a vigorous
apical bud is encouraged at each pruning.Numerous small branches are encouraged to grow
along the upper portion of the central leader.These branches are restricted by heading them
back.This prevents overgrowth of the top of the tree and allows excellent light penetration into
the lower canopy.

Well-feathered nursery trees are best for establishing the central leader orchard (Figure 2).After
planting, remove low and undesirable branches, top the tree at 48 inches (just above a healthy
bud oriented into the prevailing wind) and stub as many as eight well-spaced, healthy branches to
two buds.Summer pruning is done 6 to 8 weeks later, after growth has initiated and shoots have
begun to elongate.Undesirable growth below the lowest scaffold and upright shoots from the
scaffolds are rubbed off.The leader is singled out and growth from the scaffolds is directed
outward.Use caution to remove as few shoots as possible to avoid removing too much leaf
surface.

The important cuts to make when pruning the following spring, year 2 (Figure 3), are heading
back the leader to a strong bud, removing branches competing with the leader and spacing the
scaffolds properly along the lower trunk.Additional cuts may be necessary to direct the growth
of the scaffolds outwards.It is important to summer prune as in the previous year.

The 3-year-old tree (Figure 4) is ready to produce its first major crop.Training cuts are needed
for structural purposes but also to establish good conditions for development of the crop.In
addition to the types of cuts made the previous year, it is necessary to select fruiting laterals in
the upper portion of the trunk.At this stage, it is important to direct terminal growth of the
scaffolds laterally.Again, summer pruning is necessary to direct growth from the scaffolds
laterally and to remove unwanted upright and vigorous growth.

By the fourth year, the structure of the tree should be established and there is a large enough
potential canopy to support nearly a full crop (Figure 5).As in other years, it is necessary to
maintain the upright growth of the leader, remove branches competing with the leader, restrict
the growth of the branches on the upper trunk and, most importantly, direct the growth of the
scaffolds outward.Be sure to eliminate competing scaffolds.Summer pruning will continue to

be useful to remove vigorous competing growth that shades the “working leaves”on the fruiting
wood.

Pruning the mature tree follows the same principles.A careful balance is required to restrict
growth from the upper portion of the tree without serious reduction of the vigor of the central
trunk.Heading back cuts may be necessary to maintain the tractor aisle and restrict overlapping
of the trees.Care should be used when summer pruning so that tree vigor is not reduced
excessively.

IMPROVING PRODUCTION EFFICIENCY
OF CENTRALLEADER ORCHARDS
Cooperatively with three growers and one nurseryman, we are developing management
proceduresto improve the productivity of central leader trained peach and nectarine trees.
Spacing and nitrogen fertilizer rates are being compared.The varieties included were Vinegold,
Virgil, and Babygold 5 processing peaches and Harblaze and Fantasia nectarines.All were
propagated on Bailey rootstock.The experimental plots were one acre in size.

Trees were spaced at either 1.4, 2.3 or 3.5 m (4.5, 7.5 or 11.5 ft) apart in the rows, which are
spaced 5.5 m (18 ft) apart with 1329, 798 and 519 trees/ha (538, 323 and 210 trees/acre),
respectively.The trees spaced 7.5 and 11.5 ft apart were pruned as 4-scaffold central leader trees
as described previously.Trees at the closest spacing will be pruned as 2-scaffold trees
(Figure 6).The concept of pruning is the same, but only two scaffolds will be permitted on the
mature trees, both oriented into the aisle between the rows.

Nitrogen fertilizer application rates are 100, 50 and 25% of the amount recommended for
commercial peach production in Ontario (Ontario Ministry of Agriculture, Food and Rural
Affairs, 1998).It was applied at bud break as a granular fertilizer (ammonium nitrate) to the soil
surface at the drip line of the trees in 1997 and 1998.No fertilizer was applied during the
planting year, 1996.Recommended amounts of potassium fertilizer were applied in the same
manner.Other orchard management and integrated pest management procedures were standard
for commercial orchards in the area.

The trees were planted in the spring of 1996 and records of growth and fruiting have been
maintained.Information presented is for only one variety, Vinegold, and at one cooperator’s
orchard (Smith).It is representative of data from other varieties and at other orchard locations.

Tree growth in all varieties and orchards has been vigorous.The average height of the Vinegold
trees at the Smith orchard at the end of the third growing season, 1998, was 3.35 m (11 ft) and
the spread was 3.05 m (10 ft) (data not included).Trunk cross-sectional area (TCA) after the
third growing season was affected minimally by rates of fertilizer application (Table 1).The
sandy loam soils of the orchard site supported strong tree growth during the early development
of the orchard with minimal rates of nitrogen fertilizer.No nitrogen was applied during the
planting year.The TCA of the more widely spaced trees at 11.5 ft, tended to be larger than the
TCA of the closer spaced trees at 4.5 ft.These differences in tree sizes occurred mainly during
1998 when competition among trees was greatest at the closer spacing (Table 2).Also, trees at
the closer spacing were trained with only two scaffolds, which required the removal of more
wood during pruning.