The removal of leaf bearing branches to leave structural limbs as re-growth point
If pollarding is to be carried out, it should preferably start soon after the tree has become established and is between 25 mm to 50 mm in diameter at the selected height of pollarding (often 2 m to 3 m).
The initial pollarding cut should be made at a height which reflects site dynamics but which, if possible, allows some of the pre-existing foliage to be retained, in order to maintain physiological function and thus
reduce the probability of dieback or death.
If the tree divides into a number of stems or branches below a height of 3 m, these should be individually cut so as to initiate a “candelabra” framework.
If the stem has attained a diameter of more than 50 mm, but less than about 200 mm at 2 m to 3 m height, pollarding may still be initiated. The tree should be cut at or near the same height as a younger tree, but extra care should be taken to retain some existing branches. Larger trees should not normally be treated in this way
Once initiated, a pollard should be maintained by cutting the new branches on a cyclical basis. The frequency of the cycle should be decided according to site management objectives, species, age, condition and/or
any product that might be required. Selective cutting, whereby some of the pollard branches are retained within each cycle, should be chosen if this would help to prevent dieback and decay in the stem.
Branches that grow after pollarding should normally be cut at their
bases in order to encourage the formation of a knuckle after a number of cycles. If, however, the pollard cycle has been allowed to lapse over many years, the crown should instead be reduced to the minimum necessary to fulfil current objectives. i.e. the relief of any mechanical stress that would otherwise be likely to cause
the stem to split apart.
Even if the stress on an old pollard branch is severe, it should not be cut back to the knuckle, since the removal of all its attached foliage would probably lead to physiological dysfunction and decay. It should instead be shortened by cutting just above a suitable lateral branch, or failing that, by retaining a live stub from which
new shoots could grow.
If crown reduction would be insufficient to safeguard those branches that are most likely to fail, they may be reduced to stubs in one operation (a “pole thin”), while the remaining branches are shortened so as to retain enough of the leaf-bearing twig structure to sustain the tree[s] retention .