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The most commonly planted broadleaved trees in Ireland are ash, sycamore, oak and beech. The lower section of the trunk is the most valuable part of these trees. This is the portion of the tree, which yields the greatest financial return. Particular attention should be paid to stem quality over the first 4 years during which time stem height is likely to reach between 2.0 to 4.0 metres. A quality stem in a young broadleaved tree is one which is straight and unforked, with no particularly heavy branches distorting it.
What is formative shaping?
Formative shaping is a management operation carried out in the very early years of growth of a new plantation to ensure that sufficient young trees produce a straight stem with a single, straight dominant leading shoot. Formative shaping is concerned with retaining this shoot and removing all other shoots and branches, which might compete with or damage it.
Shaping begins in the second year after planting when the tree is 0.8 to 1.2 metres in height and continues until the tree is 5 to 6 metres tall. To achieve good results it is important that a leading shoot is chosen which will give the strongest, straightest stem and all shoots competing with this leader should be removed or trimmed in one or more operations.
How many trees to shape
Recent research has shown that it is better to concentrate on the larger trees in a plantation. These trees are naturally faster growing and will pass out and suppress their slower growing neighbours. However, there are some large trees, normally called “wolves” which have very poor form and tend to take up a lot of space. As these stems will be removed early in the life of the crop there is little point in wasting time shaping them. The message is to concentrate on trees with better quality stems, which are average or above average in size.
How to shape
The key element in formative shaping is to favour the development of this one single, straight, leading shoot. A secondary process is to remove all excessively large branches, which could cause problems for the main stem. Both processes are carried out at the same time.
Where a tree has forked, shaping consists of removing the weaker or poorer quality shoot (See Photo 1). If not removed, this fork will remain at the same height on the tree for its lifetime. Where the problem is a group of more or less equal shoots at the top of the tree all - except the straightest shoot - should be removed. But where this might involve the removal of too great a portion of the foliage, only the largest competitors are removed in that shaping operation.
Any side branch low down on the stem, which is more than half the diameter of the main stem, should be removed. In most cases, timely formative shaping will prevent the development of such large branches.
Where to make the cut
It is vital not to cause injury or allow disease to enter the stem of the tree when making shaping cuts. It is also important to produce a clean smooth cut outside the Branch Collar. This is usually a wrinkled swelling at the base of the branch, where it joins the main stem (See Photo 2). The cut must be made just outside this collar without damaging it. This prevents loss of timber value due to wood discolouration and diseases. Do not leave “branch stubs” which take a long time to heal over and result in “black knots” in the timber.
Saws or secateurs
Early formative shaping is carried out using garden secateurs (by-pass model), which will easily cut branches up to 2 centimeters in diameter. If shaping is not carried out at the appropriate time you may find that you need to use a special small pruning saw or loppers for most of the work.
Do not over-prune
It is important to keep a balance and not to “over-prune” by removing too many large branches. However, recent research has shown that it is better to prune and remove all potential defects than to leave them. Such hard shaping or pruning can remove a lot of branch and foliage – in some cases more than 50 percent – without damage to the welfare of the tree.
When to shape
The best time for formative shaping most species is mid June and July. At this stage damage from winter and late spring frost will have shown up (See Photo 3). If shaping is not possible at this time, it can be carried out in mid-winter (the recommended time for oak). Early pruning is essential because trees recover their shape and straightness much more readily when shoots are soft and malleable. It is also much easier and cheaper to prune smaller and softer branch material.
Ongoing Shaping
The first stage of formative shaping can produce trees with a single straight stem up to 3 or 4 metres. But damage may set in again on some stems just above the height to which shaping has taken place. It is very important to continue the process again concentrating on the best and tallest stems and to manage these stems up to 6 metres, which is the target height for the shaping operation in broadleaves (see photo 4). Most broadleaved crops will need at least two shaping operations spread a couple of years apart. Where possible, it can be very beneficial to do some formative shaping each year until trees have reached the required height.
Grant aid may be available for shaping broadleaf trees. Contact your nearest Teagasc Forestry Adviser or Forest Service Inspector for details.
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