Quote:. . . moderate density orchards, if well managed, can match higher density orchards for
production and, when mature, are much easier to manage.

Planting Decisions from the New Zealand Perspective

John Wilton
Deciduous Fruits Specialist
AgFirst Consultants Hawke’s Bay Ltd.

Reprinted with permission fromThe Orchardist(NZ) 70(4): 10-13, May 1997.

The rootstock, planting distances, site vigor and cultivar factors are up for discussion at early
stages in the planning program.Unfortunately, there is no recipe which can be followed so each
of these factors needs to be carefully considered when designing the new orchard planting.The
skill lies in integrating all these factors and then adopting management policies which fit the
situation.

Whatever planting system is chosen, the final result will be totally dependent on how well the
trees fill their allotted space with balanced growth and strong healthy fruit bud.Its long-term
future will depend on how well you maintain the optimum vigor/cropping/light interception
balance throughout the life cycle of the block.For financial success, the main focus needs to be
sustainable production of high quality fruit at maximum yield.

Relative to the benefits of maximizing income through high orchard performance, any benefit
which can be obtained by shaving costs is minimal.This does not mean spending extravagantly
on exceptionally high tree densities or fancy trellis systems.But it does mean spending what is
necessary to get the basics right.

PLANTING DISTANCES
This is a controversial question at any time.Largely it depends on the likely vigor of trees
planted in a particular site.Vigor varies with rootstock/interstock, scion, topsoil depth and
whether or not the site is a replant one.A certain amount of vigor manipulation is possible so
each rootstock/scion combination has a range of tree density over which it can be managed
reasonably successfully.

Between-row spacing also has to take machinery access into account as well as tree vigor.With
the present standard New Zealand bin of 1.07 x 1.5 m (3.5 x 5 feet), spacings below 4 m (13 feet)
between rows become very difficult and, if you want an easy life as a tractor driver, 4.5 m
(14.7 feet) between-row spacing becomes about the minimum acceptable distance when orchard
access is taken into account.If you want narrow rows, you need to adopt a smaller bin.In-row
spacing, as far as I can see, should not be less than twice the distance of 2 years’ extension
growth.At twice 2 years’ extension growth, the side branches along the row from adjacent trees
will be touching at the end of their second growing season in the orchard and therefore filling
their allotted space.As a rule, you do not carry good fruit bud until the wood is 2 years old
which means that it will be in the third leaf before sufficient crop load can be applied to bring
vigor under control.

ROW DIRECTION
Row orientation also affects in-row spacing.Where row direction is more or less north/south, in-
row spacing can be close because each side of the row gets equal levels of light.Once rows
approach east/west direction, the south (north in the northern hemisphere) side of the tree
becomes very shaded and produces poor quality fruit unless there is sufficient gap between the
trees to allow good light to get through to the shaded side of the row.The best way to achieve
this is by having greater in-row distance to give light access to the shaded side of the tree.If you
do not, it is likely that most of the fruit will be carried on the sunny side of the tree where it has a
high risk of becoming sunburned.

To minimize sunburn problems a row orientation that allows the sun in the early afternoon,
which is the hottest part of the day, to shine straight down the rows will give the least amount of
problem from sunburn.A stake or post will cast a shadow which can be used to check row
orientation.In the winter the shadow cast between 1:30 p.m. and 2:00 p.m. will give the
optimum row direction to minimize sunburn problems.During the daylight saving period, look
at the shadow between 2:30 p.m. and 3:00 p.m. for optimum row direction.

TREE HEIGHT
With tree height you need to compromise between yield efficiency and ease of working and
spraying.There are a number of studies which indicate that for optimum yield the ratio between
tree height and between-row spacing should be in the range of 0.8:1 to 1:1.With high light
levels and relatively low latitude in New Zealand compared to northern Europe, ratios of 1:1 are
more suited to our situation if yield is to be maximized.In fact if you have badly misjudged tree
vigor, it may be necessary to exceed the 1:1 ratio to obtain satisfactory balance between
vegetative growth and cropping.

Trees to about 4.5 m (14.7 feet) height are relatively easily worked from 8-rung ladders which
means that, in terms of tree height, 4.5 m between-row spacing is about right.With dwarf
rootstocks, between-row spacing needs to be less if tree height to between-row ratios of 0.8:1 or
1:1 is to be achieved, otherwise too much of the orchard is devoted to tractor access.

For New Zealand conditions the optimum tree dimension, if we had the right rootstock range
(generally MM.106 in New Zealand) and sufficient knowledge of behavior of the scion/rootstock
combination under the conditions at which they are going to be grown, would be 2 to 2.5 m (6.6
to 8.2 feet) spread and 4 to 4.5 m (13 to 14.7 feet) height.These trees would be grown in the
range of 890 to 1250 trees/hectare (350 to 500 trees/acre).

Where excess vigor is likely to be a problem, e.g., MM.106 on new soil, M.793 on fertile replant
sites, we need to think more conservatively on tree spacings and here 5 x 3 m (16.4 x 9.8 feet) is
possibly the safest option.

With dwarfing rootstocks, particularly Mark and M.9, tree densities need to be in the range of
1500 to 2000 trees/hectare (607 to 810 trees/acre), i.e., 1.65x 4 m (5.4 x 13.1 feet) to 1.45 x
3.5 m (4.7 x 11.4 feet) in order to fill their allotted space efficiently.Once you drop below 4 m
between rows, we are committed to narrow equipment, including bins.Also with dwarf trees,
you drive between rather than under the trees because it is difficult to get sufficient tree height to
pass under the lower branches.

EARLYYIELDS CRITICAL
With any new development, or a replant situation, early yields are critical to the financial success
of the venture.There are a number of ways of cracking this nut.Up to a point planting higher
density orchards will achieve this objective but it can be expensive.Also as the orchard matures,
high densities may lead to real orchard management problems if vigor cannot be controlled and
shadeout from overcrowding occurs.

In my opinion moderate density orchards, if well managed, can match higher density orchards
for production and, when mature, are much easier to manage.This path also enables us to stay
with woolly apple aphid tolerant rootstocks rather than turn the clock back 100 years and move
back to rootstocks which lack woolly apple aphid resistance.(Editor’s note:All MM. rootstocks
are resistant; root infestations with susceptible rootstocks are not generally a problem in North
America.)

The first step in obtaining high performance from a moderate density orchard is to plant a large,
well-grown tree.I am aware of a number of blocks which have been planted with 2-year-old
scion trees.These trees already have a good lower branch structure in place.When planted they
will go about three-quarters of the way toward filling their “in-row”space with fruiting wood if
placed around 2 m (6.5 feet) apart in the row.The transplanting shock also tends to reduce tree
vigor and encourages flower development with those varieties that are tardy at producing flower
buds.With this type of tree I have seen about half a box of fruit taken in the first growing season
without compromising tree development.In the second growing season, yield can be around 1 to
1.5 boxes and I suspect, by year three, 2.5 boxes a tree would not be impossible.

If you planted at 2 x 4.5 m (6.5 x 14.8 feet), the first year production would be 550 boxes per
hectare, with 1650 boxes per hectare in the second year and somewhat above the national
average at 2775 boxes in the third leaf.

The key is to plant a big tree and keep it growing.Early planting is preferable, by mid-July
(midwinter in New Zealand) if soil conditions permit.However, I have seen high growth
performance from September/October (spring) planted trees where satisfactory irrigation
management has been practiced.

WEED, PEST AND DISEASE CONTROL ABSOLUTELYVITAL
Apart from early season water stress, there are two other factors which stop young tree growth
stone dead in its tracks.These are weed competition and foliage loss due to pests, diseases or
misguided summer pruning.Weed control in the young orchard has to be immaculate to
optimize early production.In replant blocks or near established orchards in New Zealand, apple
leaf curling midge will devastate new growth if left uncontrolled.Black spot (scab) and powdery
mildew are capable of doing a similar job if not controlled.As young tree growth extends well
into the autumn, the growth is at risk from leaf curling midge, black spot and powdery mildew
until it ceases and the terminal leaves become mature.

At a rough guess, getting the weed and pest and disease control right for the first year in a new
planting will probably cost only about NZ $1000 per hectare (US $500 per acre), but will
probably more than double tree growth.This means that, in terms of yield performance, well-
looked-after trees will more than compensate for going to much higher densities.If good pest,
disease and weed control costs only about NZ $1000 per hectare, this amount will buy you only