Structural Pruning: A Tree That Does Not Break in Wind and Snow

Most urban trees in Iran are pruned after a branch breaks, not before. Structural pruning is a different job: in the young years you build a framework with one clear axis, fewer competing co-dominant branches, and no unions left with included bark. The result shows ten years later, when the spring gale or the light snow load of Tehran and Shahrekord arrives, the topped neighbour breaks, and your tree merely sways. Farkesht treats this pruning as part of maintenance, not as crown styling for a photograph.

One leader, a clean union, no topping

Many shade species in Iran, left alone, build two or three stems of equal diameter, and at the fork the bark folds inwards. That union opens under wind loading. The aim of pruning in the young years is to keep one temporary or permanent leader clearly defined, and to remove the competing branch or reduce it to a lateral. Topping is the opposite of this logic: you cut off the tip of the axis, dozens of whips grow from the ring of the cut, and every whip has a weak attachment. On Iran's urban plane and mulberry trees, annual topping is precisely a factory for hazardous branches.

• Keep one dominant axis as far as the species allows; ash and plane follow this pattern well.
• Remove a branch with included bark early, while its diameter is still less than half the trunk's.
• Do not take more than about a quarter to a third of the foliage at any one time, or the tree is provoked into emergency shoots.
• Never square the crown off like a concrete column; read the natural form of the species.

Cut outside the collar, not flush and not leaving a stub

The branch collar is that slightly swollen ring at the union. The cut has to be outside that ring so the tree can close the wound. A flush cut takes the collar away and makes a big wound; leaving a thirty-centimetre stub also brings decay and produces weak buds. The saw must be sharp and the bark below the cut must not tear. On old trees, if you must remove a thick branch, use a three-cut sequence so the trunk bark does not strip. Wound paint and sealant are unnecessary in most cases; a clean cut matters far more than tar on the wound.

Timing: dormancy against summer

For most deciduous shade trees, the main structural pruning is done in dormancy: after leaf fall and before bud swell. The framework is easier to see and sap flow interferes less. The exceptions matter. Species that bleed heavily in spring are better pruned after the leaves are fully out. Trees that flower on last year's wood lose that year's flowers if you cut them hard in winter; for those, light pruning after flowering or removing only dead wood is the sensible course. Do not prune heavily at the height of July and August: trunk sunscald and the attraction of wood-boring pests both rise. Keep summer pruning to thin deadwood and hazardous branches.

Little each year on a sapling, deliberate work on a mature tree

Do not prune a newly planted sapling hard in the planting year; take off only broken branches and competitors on the trunk so the roots can feed the crown. From the second to the sixth year, make two or three small decisions each winter: the leader, the spacing of the main branches along the trunk, and the removal of one bad union. A twenty-year-old tree cannot be turned back into a sapling in a single session. There the aim is safety: reducing the lever of a long branch over a building, opening a dense crown, and taking out dead wood. Spread the reduction of thick branches over two or three years so the tree does not fill with whips.

1. Year one: only transport damage and branches dragging on the ground.
2. Years two to six: choosing the leader, vertical spacing of the main branches, removing small pockets of included bark.
3. Maturity: monitoring weak unions, reducing weight at the branch tips, keeping the species' form.
4. After every gale: inspect for cracks and hanging branches before any cosmetic pruning.

Pruning safety matters more than the tree

If structural pruning is being done on a tree beside a walkway, you have to close the route, prevent branches falling on pedestrians, and take the clearance to power lines seriously. A chainsaw on an unsupported ladder causes an accident every year in the lanes of Isfahan and on the medians of Tehran. If a branch is on a wire, the electricity authority comes first and the saw second. Helmet, eye protection and rope are not recreation for work at height. The Farkesht team does not work above four metres or near utilities without a safety plan, and expects the same from the owner. At home, if only thin deadwood is within arm's reach, take that off and leave the rest to a team. A hired chainsaw on a green branch under load damages both the tree and your spine. Structural pruning is precise work; rushing to tidy the yard before guests arrive is usually the very topping that has to be corrected more expensively next year.

A simple programme for a yard or a factory landscape is to review the framework once each winter and look only for deadwood each summer. Note which branch became a competitor to the leader this year and which union carries included bark. A photograph from a fixed angle each March shows progress or regression. Look at a tree the way you look at a building project: framework first, façade second. If the framework is crooked, no fertiliser or irrigation will make a weak union strong. For urban plane and mulberry trees that have already been topped, expecting a return to natural form in one season is unrealistic. Over two or three consecutive winters, thin the weak whips and keep a few better-attached branches as the new framework. Rushing to give it a shape is the same vicious circle of topping. If you see a large fork with included bark on a mature tree and there is a building under it, decide between cabling and removing the branch; ignoring it is not structural pruning, it is a bet.