This
sheet is designed to assist growers in the pruning of their olive
trees during the first two years after planting. The information
given is for trees between approximately 300mm (1 ft) and 1.5
metres (5 ft) in height. During this fast growth period the trees
require specific pruning to maximise their growth, keep
them in good health, and very importantly, prepare them for mechanical
harvesting. The briefness of this sheet cannot give all the answers
and options but it does give a basic guide to pruning and
staking during the first couple of years.
Whenever
you are pruning a young olive tree there are four main points
to keep in mind:
1.
Too much pruning at a young age will stunt the tree's growth.
2.
You are ultimately wanting to prune for mechanically harvesting
the crop.
3.
A central leader trunk will assist growth in the early stages.
4.
Practice makes perfect!
Let's
take a closer look at these points.
1.
BODY TALK - Olive trees are like human beings in many ways
and in no way are they so similar as in the pruning. It's as simple
as this:
A
human can afford to lose an arm or even a leg and
still live reasonably well BUT if you lose both arms and both
legs
at the same time, you're in trouble! - SO IS AN OLIVE TREE.
If your young
tree is 900mm (3 ft) tall and has side branches growing all the
way up its trunk DO NOT take them ALL off just because you've
read that you need a clean straight trunk for 1.0 to 1.2
metres.
At
first, only take off any that are growing below 300mm (1 ft) and
then in several months time when the tree has grown considerably
more on top, and has 'recovered' from the first pruning, you can
take off any branches between 300mm and 600mm (1-2 ft). Repeat
this process until finally after about two years, you have your
clean straight trunk for 1.0 to 1.2 metres. Don't make the mistake
of pruning 'too much too soon'. This can send the young
tree into 'shock' and set it back by up to a full year. Always
leave large amounts of leaf on the tree for photosynthesis
to take place so that maximum root growth etc will occur.
2.
Mechanical harvesting is the most efficient method of removing
fruit from olive trees. Whereas oil olives have been the only
mechanically harvested olives for many years, table fruit are
now sometimes dropping into catching umbrellas in countries
around the world, including Australia. Unless you have made
a clear decision to hand harvest your fruit, to neglect pruning
for future mechanical harvesting in the modern orchard may be
a serious error from a long term economic viewpoint.
So
what shape of tree do we need for mechanical harvesting? The most
important requirement is a straight trunk for 1.0 to 1.2 metres
(3'4"-4 ft) from the ground. This section of trunk must finally
be free from all branches to allow the harvester's head to securely
grip the trunk without any obstruction. This will allow the harvester
to work more quickly and will also avoid damage to the tree.
Achieving
this straight clean trunk occurs over about 18 months to two years.
Initially, when the tree is only 300mm to 600mm (1-2 ft) tall
you simply need to remove any branches which want to grow off
the trunk below 300mm (1 ft) from the ground. Other branches above
300mm (1 ft) can be left to grow or, if they try to grow
larger and faster than your main leader, they can have their tips
removed to slow down their growth - thus allowing more nutrients
to be focussed into the leader. This clearing will make
it easier for weed spraying and will also allow the tree
to focus all of its growth into the main 'leader' trunk and some
higher lateral branches. At no stage should any growth touch
the ground. In the early years, it is important to leave as much
growth as possible on the tree because foliage promotes
root growth which in turn promotes the production of more foliage.
Some
trees will develop with a 'leader' (trunk) going straight up the
centre with small side branches. Others will head straight for
the sky as a single trunk with no side branches. Both cases
are fine, but with single trunks you will need to nip off the
growing tip at about 1.2-1.3m (48-50") to encourage
side or lateral branches to grow at this place. It is these lateral
branches that will form the main structure of your mature tree.
(For notes on another pruning method see OLIFAX
- 9 'Monoconical Pruning')
Mature
olive trees need to be kept reasonably open in the centre to allow
light penetration for better tree health and fruit production.
This is best achieved through a vase shaped, sturdy growth
habit which also facilitates mechanical harvesting. Your
trees will probably have quite a number of lateral branches
at about one metre or so from the ground when the tree is 18 months
of age. Thoughtfully choose out four evenly spaced lateral
branches. These need not all come from exactly the same
height but should not be any lower than 800mm from the ground.
As these will form the vase framework for your tree, if
possible choose branches that are growing at least 30 degrees
up from horizontal. This will give a vase rather than a
flat plate shaped tree structure. Remove the other growth
as outlined below.
If
your main leader is damaged or slow growing for some reason then
you may choose to allow a faster growing side branch to
become the new leader. Simply remove the old leader from
the stake and tie the new leader to it. (A bit like politics!)
When
the tree is between 900mm and 1200mm (3-4 ft) tall, and if it
has plenty of leafy branches towards its top, you can remove
the branches which are growing from the trunk between 300mm
and 600mm (1-2 ft) from the ground. You should now have a tree
with a straight clean trunk to 600mm (2 ft) and a nice number
of branches above 600mm (2 ft). If your tree is over 1200mm
(4 ft) high then you can remove the tips of any branches
that leave the trunk between 600mm and 900mm (2-3 ft). (Don't
forget BODY TALK's advice - if there aren't many branches between
900mm and 1200mm (3-4 ft) then don't cut too heavily at this stage).
Several
months after you have done the last step of pruning above, you
can remove any of the final branches up to about one metre (3'4").
Your trunk is now clean to the desired height for machine harvesting
and yet you still have about four evenly spaced solid branches
at the top of the tree to keep root growth to a maximum.
Depending on variety, land preparation and climate this whole
pruning cycle from a 300mm (1 ft) tall tree to a solidly trunked
tree which is branching well on top should take about eighteen
months to two years.
STAKING
YOUR TREE
The
staking of young olive trees is very important. Stakes need to
be strong enough to support the tree while the anchor roots are
developing, and yet flexible enough to allow the tree to
move in the wind. If the stake is too rigid or the tree
tied too tightly to it, then the tree will be over protected and
not feel the need to develop strong roots. The small bamboo stakes
supplied with the trees from the nursery will only support
them for a short period.
Olives
Australia has been recommending the use of bamboo stakes for sometime.
The most common size to use was the 1.5 metre (5 ft) high, 16-18mm
thick. Bamboo stakes are considerably cheaper than hardwood
stakes but, in windy areas, some of the stakes may have
to be replaced due to breakage. Thicker stakes are available:
1.8m (7fr) high, 25-28mm for .77ยข each including GST + delivery.
The
bamboo stakes have some advantages over hardwood stakes as they
have a smooth surface and do not damage the bark or rub out newly
forming buds, which are going to be the scaffolding branches
of the tree. They also allow the tree to flex in the wind thereby
encouraging the tree to develop a thick trunk and also to
develop its anchor roots quickly. A tree rigidly tied to an unbending
hardwood stake will not realise the need to develop its anchor
roots strongly. The bamboo stakes are also easy to handle,
eliminating splinters and the lifting of heavy bundles.
Sourcing
Stakes - Stakes are available from Olive Agencies.
Thicker
stakes of about 24-26mm can last up to two years at which point
the tree will no longer need staking. It is rare for a tree
to need any support after it has outgrown such a stake. Place
the stake about 50mm (2") from the base of the tree
and push it into the soil at least 300mm vertically until it
feels quite stable. A better option is to use the stakes to mark
your tree sites prior to planting and then simply plant
the trees beside them. You can then tie both the young tree and
its small nursery stake to the main stake with a tool such
as the tapener described below. (There is no need to cut off the
the tapes between the young tree and its nursery stake as
they will break away naturally as the tree trunk thickens.)
After
planting and staking the tree, the stake will prove to be a good
solid anchor point to attach protective guards or netting to if
you have severe animal problems and do not have a full netting
fence around the boundary of your orchard.
Tying
the Tree - From our experience with tying methods over many
years, we have found that the tape tying tools available from
Olive Agencies are an excellent investment. The taping tool is
very fast and efficient and if you have a number of trees to tie,
you will get the cost of your tool back very quickly in
saved time. When you order your tool Full
Staking Kits are available which include a packet of
staples, a packet of spare cutter blades, and unless you
have very thick trunks, the 26 metre rolls of tape will be what
you'll use.
After
testing many brands of tape, we recommend the high quality, green,
Italian tape which we now stock as standard. As the tree trunk
grows thicker it will be better able to support itself without
so much need for the stake. As the trunk thickens, the tape
will stretch and naturally tear out at the staple point so it
will not strangle the tree as some ties do.
The
tree will eventually get to the stage where extra support is needed.
Ties
or Tying
Cord are available which are positioned at the top of the
stake and then the Olive Taping tool is used to tie the rest of
the tree.
3.
A central leader trunk will help to speed up your tree's growth
during the early years. Because this trunk will be fast growing
and always growing upwards in the centre of your tree, it will
be drawing nutrients up through the tree to sustain its
growth. As it draws these nutrients up the tree, the nutrients
will be carried to lower branches and thereby increase their speed
of growth as well. The central leader acts as a type of 'nutrient
pump' within the tree. (If your tree decides to grow straight
up without any lateral (side) branches, nip the growing tip out
when it reaches about 1.2 - 1.3 metres (4 ft). This will force
it to start lateral branching into your vase shape.) Don't get
this central leader method confused with monoconical pruning (OLIFAX
- 9).
What
we have finally achieved is a young tree with approximately four
main scaffold branches. The shape is commonly known as an Inverted
Conical Vase.
As
mentioned in the introduction, this is not a conclusive pruning
guide. It only touches on the basics of pruning young trees with
what are considered the most commercially viable methods.
4.
Practice Makes Perfect! Olive trees have a mind of their own
and as such they will sometimes fight against many of your
efforts to prune them into shape. Don't give up. Perseverance
wins the race. Remember that time is on your side. A tree
that won't grow correctly this season can often be restaked and
then pruned into shape next season.
