WORKSHOP NOTES onTree Behaviour and Reaction to Pruning (Spur bearing Apple and Pear Trees).

These notes are to go with my tree pruning workshops and are for revision purposes for those who have attended these. I hope that they will also help newcomers to pruning.

What we want is a calm, long-lived healthy tree with plump ripe fruit. What it wants to do is be an unruly skyward reaching tree with large crops of small fruit. To get what we want we need to control its vigour, maintain a constant renewal of its branches and create a light and airy environment for the fruit to grow in.

Pruning is all about taking advantage of and moderating the tree’s natural growth habits. To do this it is necessary to understand some of the natural ways of the tree in order for us to know how it will react to what we do and so we have some control over its ways.

The Apical Buds: (at the tips of the branches/shoots)

• Are responsible for lengthening branches/shoots
• Inhibit growth of new shoots further back by producing a growth inhibiting hormone that flows down the cambium.
• Have more influence on both shoot lengthening and side shoot inhibiting the more vertical the branch/shoot is.

So we can:

ü  Cut them off to reduce shoot lengthening.

ü  Cut them off to promote side shoot growth.

ü  Force the branch/shoot to a more horizontal angle to reduce apical bud influence and so slow lengthening and promote side shoot growth.

ü  Cut a “notch” under the apical bud to reduce the flow of its inhibiting hormone down the shoot and so encourage side shoot growth.

ü  Cut a “nick” above a bud that we want to free from the apical bud’s inhibiting hormone so it can grow into a side shoot.

ü  Cut the branch/shoot at a union with another so that the remaining one’s apical bud inhibits side shoot growth.

Vegetative buds: (small, triangular or pointed, flat against the stem)

• Grow to form new shoots in the direction that they face on the branch or shoot.

So we can:

ü  Cut to a vegetative bud to fill a gap in the tree.

ü  Cut to a vegetative bud to create more horizontal or vertical branches.

Fruiting buds: (store carbohydrates for flower development so are larger and fatter – and furrier)

• Develop on two year old wood and flower/fruit the following year.
• Need sunlight otherwise they wither and die.
• On spur bearing fruit trees extend to form spurs and divide to produce two flowers, and so on every year creating a complex crowded system that produces lots of small fruit.
• When released from apical bud dominance they do not grow into new shoots.
• At the end of a shoot they stop it growing longer.

So we can:

ü  Prune to a fruiting bud to avoid shoots re-growing and ensure energy goes to fruiting.

ü  Prune spurs so there are fewer but good sized fruit.

ü  Prune tree to ensure fruiting buds get a light and airy environment.

Branches:

• Generally have an inclination to grow upwards which leads to a narrow angle between the branch and trunk which is weak and breaks under the weight of fruit or in high winds.
• That are more vertical have more vigorous growth and are less fruitful.
• Need to have sap pulled along them by vegetative growth in order to stay alive.
• That are horizontal tend to produce fast growing vertical watershoots.
• That are at 45-60 degrees are best for a balance between fruitfulness and vigour and are strong.
• Form a layer on lignin around them every year which strengthens them in the position they are in over that year.
• Have a branch collar which actually is part of the stem they come from and has healing properties.

So we can:

ü  Try to create branches at good angles by physically forcing them to grow at the desired angle when young by tying, weighting down, tucking under another branch or with the use of spreaders. The weight of fruit will often do this for us.

ü  Avoid cutting branches to points where there is not enough vegetative growth to keep what remains alive. Do this by cutting to unions with side branches, a general rule of thumb is that the side branch’s cross section should have at least a third of the area of the  cross section of the branch that is being removed.

ü  Avoid damaging the branch collar

Shoots:

• When cut to a vegetative bud give more shoot growth, in the direction that the bud and one below are facing so try to choose two facing outward and to the sides rather then two where one will grow into the centre of the tree.
• When cut to a fruiting bud stop the shoot from putting on more vegetative growth and forces it to expend energy on fruiting.(If the bud is pollinated and turns into a fruit)
• When cut to no bud die between the cut end and the next bud down. This creates a “snag” where diseases can enter.
• React to pruning in that the more you cut off a shoot the more relative growth you get. This is counterintuitive to what you want to do in practice.

 So we can:

ü  To some extent control the number of branches/shoots grown and their direction of growth.

ü  To some extent control the number of fruiting shoots.

ü  Promote growth by hard pruning weak shoots (up to a half of the last year’s growth).

ü  Limit growth by gentle pruning of vigorous shoots (up to a third of the last year’s growth of just a few buds removed if growth is very vigorous).

ü  Reduce unwanted new growth by making fewer, but larger, cuts.

Watershoots: (vigorous upright shoots)

• Often form as a reaction to damage/cuts.
• Often form on horizontal or drooping branches.
• Do not return when torn out, when young, in the summer.

So we can:

ü  Tear off new watershoots in summer (late July – mid September). Unless we want them to form a new branch.

ü  Keep the number of cuts to a minimum.

ü  Ensure branches are at an upward angle.

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