Establishing the High Density Supported Apple Orchard

Part 5: Training High Density Apple Trees

Table of Contents

1. Training the Slender Spindle
   1. Planting Year
   2. 2nd Year
   3. 3rd Year
   4. General Training Comments
2. Training the Vertical Axe
   1. Planting Year
   2. 2nd Year
   3. 3rd Year
3. Training on Trellis

Training the Slender Spindle (SS)

A Slender Spindle tree consists of a moderately strong central leader surrounded by weaker and more or less horizontal lateral branches. The diameter, length and vigour of these branches decreases slightly from the base to the top of the tree. The general appearance is that of a slender bell in which the basal diameter is approximately one half of its total length (height).

In developing the slender spindle tree, the goal should always be to weaken the growth in the top of the tree in order to encourage the production of fruiting laterals. As with all training systems you must build the tree one step at a time. A high level of grower skill is required to be successful with SS system. 

The support stake (post) should be put in place before, at, or immediately after planting so that the new tree can be supported right from the start. Experiences have shown that the stake should be placed 10 - 15 cm from the base of the tree and on the north side, assuming the rows run north to south.

Where wind is a consideration, trees should be planted on the downwind side and pulled back to the stake. Tie the tree to the post so that there is about an 8 cm gap between the tree and the post. Any inexpensive tying material can be used as long as it is long lasting. Speciality ties are available.

• High density supported systems require physical support for the life of the planting (perhaps 18 - 20 years). If not already in place, the support system should be put in immediately after planting. Do not allow the trees to stand free as this will lengthen the time to establishment and reduce the amount of extension growth possible.
• There are major differences in the growth and fruiting habits of apple cultivars. No single training system will be perfect as a result. As grower experience increases, different systems will prove best for different cultivars.
• The ultimate yield potential of a block will be determined by the size of canopy bearing surface.

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Planting Year (SS)

Leader Development

At 7 - 10 cm (3 - 4 in.) of new growth, select the leader and neatly cut off the 2 or 3 shoots competing with it. There is the option at this point of using the pinching technique described under the VA system. If the pinching technique is used it will need to be done several times in the early growing season. 

It is very important to emphasize growth in the planting year. Defruit at calyx to allow all trees to establish and make maximum extension growth.

 Late July (after terminal bud has set)

On trees with 2 year old lateral branches, tie down all 2 year old branches that are longer than 45 cm to a horizontal position (vigorous varieties such as Northern Spy, should be tied below horizontal).

Tying is an integral part of the SS system. Growers make money by tying to induce fruiting and there is no other way to control extension growth.

If you are not going to tie you do not want this system, proceed to VA.

Limbs that are shorter can be allowed to grow for the first season to get maximum extension growth. Such limbs left to grow, if they grow to 45 cm, should be tied down in mid August, to encourage fruit bud development. This limb positioning slows extension growth and encourages flower bud initiation followed by fruit set. 

September

Tie down any vigorous one year old lateral branches longer than 45 cm, or at least do it before bloom the following year. Limbs are usually not tied until they are 40 - 45 cm long. The lower limbs on the tree are not bent as far below horizontal as the limbs that are higher in the tree. This allows for the development of a permanent fruiting table.

The easiest way to remember is to point the branch end toward the base of the next tree trunk in the row. This limb positioning maintains the conical shape of the tree to maximize light interception and utilization. 

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2nd Year (SS)

Dormant Pruning

Remove unwanted lateral branches using a "Dutch cut" where you want a replacement limb. If no re-growth is wanted where a limb must be removed, remove with a "flush cut". If the tree is very vigorous, wait until after bloom to remove this limb. Strong growing limbs that have a large diameter and are putting the tree out of balance should be removed. Strong growth is never fruiting growth. Even if bent, these limbs are a poor source of quality fruit and should be removed. As a general rule, any branch that is 50% or greater in diameter than the point on the trunk where it arises, should be pruned off. This is referred to as the 50% rule. Upright shoots and suckers can also be removed with a flush cut at this time. 

Leader Management

In the second year, if the leader is weak, you must head it back. If the leader is strong you can "head and bag" or you can bend (do not head) so that the tip points toward the base of the next tree. If you turn the leader down you must tie something back up to the stake in late June of that year.

NOTE:

Where not enough branching has taken place (less than 4) in the planting year, the top should be regrown. When the tree is dormant cut the trunk at a point 45 cm from the ground, and restart the entire tree top. This seems like a drastic measure but high density supported systems require a "busy" tree with lots of branches. To accomplish this, the tree must be build one step at a time.

Late July and September

Proceed as in planting year. 

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3rd Year (SS)

Dormant Pruning

If you have enough lateral branches, and the leader is strong, choose a one year old limb as your new leader and remove the original vigorous leader. This zig-zag technique of leader management keeps the leader weak. This prevents the leader from quickly reaching the top of the support stack and allows for maximum limb development lower on the tree. If limb length is too long, containment is possible by cutting into 2 year old wood or to a fruit spur on that limb. Never cut to one year wood until you have studied the growth habits of your trees. Most cultivars respond poorly to this cut. If you have selected a replacement leader you must tie the leader back up in June.  

If there is not enough branching and the leader is weak, all you can do is head the leader to encourage growth or select a superior one year old branch as a new leader, tie it up and head it back. 

If there is not enough branching and the leader is strong, you can "head and bag" or bend the leader by pointing it down to weaken it. Remove unwanted lateral branches such as strong limbs (with a Dutch Cut) as described for 2nd year. Remove unwanted vertical shoots and suckers with a clean cut. Some cultivars including Gala can be pruned by using a "ripping" technique in late winter. Undesirable shoots that are ripped off don't usually support much regrowth in the area where they are removed. 

Late July and September

Proceed as in previous years.

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General Tree Training Comments (SS)

Vigour control in the slender spindle system is largely dependent upon limb positioning and early cropping. In general, the more horizontal the orientation given to a limb the less the extension growth that will occur. This limb will be influenced to form fruit buds and crop sooner than an unmanaged limb. Remember, once tied to the horizontal position, extension growth on the limb is virtually stopped. Limbs positioned horizontally before they have set a terminal bud will behave poorly and try to regrow vertically from the tip.

The material used for tying should be inexpensive, easy to knot and biodegradable by the following season. Tomato tying twine or other jute twines have been used successfully. Tree weights at first glance appear very handy for limb positioning, but accurate weight placement on the first try is difficult. Readjustment of the weights after the limb accepts the load is very time consuming.

The simplest way of tying limbs is to use a separate string for each limb tying back to the base of the post or tree. Be sure to use a loose, non-tightening loop (Fig. 6) when tying down limbs and do not double wrap the limb with the string as strangulation is possible.

Figure 6 Tree Training Knot

• Step 1: Secure end A to stake or tree trunk. Pass string over limb to be pulled down and pull to correct angle. Leave at least a 5 cm loop in string before starting knot.
• Step 2: Before proceeding pull sharply on B to transfer the loop from the B end to the A line.
• Step 3: Completed knot

In post systems, another method to consider uses a continuous string going from a galvanized nail on the lower backside of the stake to a limb then back to the nail (double wrapped on the nail) then on to the next limb and so on, until all limbs are secured. Then the knot is tied off at the last limb.

Rubber bands have been used to position first year shoots. Loop the band through itself around the leader and slip the end over the shoot to be pulled down. Take care that the end of the shoot does not go too low.

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Training the Vertical Axis (VA)

In the VA system a strong unheaded leader is encouraged to grow until it reaches 3 - 3.6 m (10 - 12 ft.) from the ground. This central axis forms a central pivot around which lateral branches radiate to form a narrow cylinder of fruit bearing wood. The diameter of the branches should gradually decrease to the top of the tree, and they should always be smaller than the trunk where located.

There should be a lessening in the length of the laterals from the bottom to the top, this results in a slender conical shaped tree. The distance between the branches should be less towards the top of the tree in order to allow for maximum light penetration.

Very little tying is practised with this system. There is more room for error in the VA system before a problem results. The level of grower skill required to be successful is less than the SS system.

The VA system can be as productive as the SS system because of the increased bearing surface. The orchard at maturity will form a tree wall as opposed to individual trees. As with all training systems you must build the tree one step at a time.

• High density supported systems require physical support for the life of the planting (perhaps 18 - 20 years). If not already in place, the support system should be put in immediately after planting. Do not allow the trees to stand free as this will lengthen the time to establishment and reduce the amount of extension growth possible.
• There are major differences in the growth and fruiting habits of apple cultivars. No single training system will be perfect as a result. As grower experience increases, different systems will prove best for different cultivars.
• The ultimate yield potential of a block will be determined by the size of canopy bearing surface.

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Planting Year (VA)

Leader Development

With the VA system the leader is pruned at planting and not touched again. In the early life of the orchard a zone identified as the production table must be established in each tree. The leader should be maintained in its vertical growth during the early age of the tree (especially years 1 to 8). This is accomplished by attaching the leader to a pole.  

It is very important to emphasize growth in the planting year. Consult "Chapter 6: Tips for Successful Establishment" for growth enhancement suggestions. Defruit at calyx to allow all the trees to establish and make maximum extension growth.

Pinching Technique

As soon as the new side shoots from the leader heading cut are 7 - 10 cm (3 - 4 inches) long, pinch out the apical bud on the 2 or 3 competing shoots and leave the leader undisturbed. This manoeuvre should be repeated every 14 days until the end of July.

The first tier of limbs should be allowed to grow at an angle above horizontal (45E) to make them vigorous and strong. Do not tie these limbs down. Very little tying is done in VA systems. Limbs below 60 cm from the ground should be removed. Secure leader repeatedly to ensure maximum extension growth.

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2nd Year (VA)

Dormant Pruning

Keep pruning to a minimum to reduce vigour. Remove upright shoots and overpowering limbs only. Remove unwanted lateral branches using a "Dutch cut" where you want a replacement limb. Strong growing limbs should be removed as they put the tree out of balance and strong wood is never fruiting wood. If no re-growth is wanted where a limb must be removed, remove with a "flush cut" after bloom. Where vigour is excessive do not remove any limbs until after they have fruited. Only summer pruning should be done in vigorous trees.

Leader Management

The leader is usually not pruned or headed to encourage maximum extension growth. This is the main feature that distinguishes VA from other training systems. However, in the second year if leader is weak you must head it back. Side shoots that compete with the leader should have the apical bud pinched (see Pinching Technique) out every 14 days to keep them weak and encourage wide angle crotches to form below. This operation begins when the competing shoots are 7 - 10 cm long. This technique does not require a heading cut to make it work.

NOTE

Where not enough branching has taken place (less than 4) in the planting year, the top should be regrown. When the tree is dormant cut the trunk at a point 45 cm from the ground, and restart the entire tree top. This seems like a drastic measure but high density supported systems require a "busy" tree with lots of branches. To accomplish this, the tree must be build one step at a time.

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3rd Year (VA)

Dormant Prune

Same as 2nd Year. Continue with the pinching technique on apical bud competition if they can be reached from the ground. Secure leader to support system. As the planting gets older it will become necessary to thin out the limbs. This thinning is done dormant and consists of removing the strongest limbs by renewal cuts (Dutch Cuts), but leaving the bottom fruiting table intact. Don't begin to thin out the bottom of the tree until fruit is higher in the tree. Remember that fruit controls growth, whereas, pruning encourages growth. You must have abundant fruit present or regrowth will be tremendous and costly. At maturity, summer pruning may be required for some cultivars where the uprights are removed to allow for greater light exposure. 

Fruit also controls tree height. The VA system should not be headed until fruit is at the top of the tree, and the leader has been pulled down with the weight of the fruit. At this point, perhaps year 5 or beyond, the top can be reduced in size to allow better light exposure to the lower limbs. 

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Training the Trellis Systems

There are many different kinds of trellis systems being used world wide. Some are extremely formal in design and require detailed timely management. Trellis systems involve the positioning of limbs along the supporting wires. This positioning can be done at any time the work load permits. Horizontal positioning is the most productive and limbs that are growing into the travel row can be either bent back in line or removed. Pruning is kept to a minimum to reduce vigour. The trees at planting are normally headed 15 cm (6 in.) above the bottom wire. Shoot growth is allowed to proceed unmanipulated until mid-July. At this time shoots are secured to the support lattice using quick, inexpensive tie materials. Upright shoots and water sprouts are removed during August to minimize regrowth and vigour. Completion of every layer is important in a trellis system. Do not allow a strong leader to reach the top of the trellis too fast. Dormant prune to a weaker leader to delay extension. The apical bud pinching technique (described under the VA system) should work well with this system. 

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