The variation in the composition of tree stands can be maintained by using a differentiated method of thinning, cutting back, pruning and leaving untouched. In older stands it is not always easy to keep this in hand: the older the trees, the more difficult it becomes. After trees and shrubs have reached their maximum height, growth tends to switch to an increase in width. Trunks and branches increase in girth and become heavier accordingly. On heempark soils with continuously high water-tables—sometimes as high as 30-35 cm below ground level—it is no less than a miracle how heavy willows, black and white poplars, ashes and oaks generally manage to stay upright. Mature specimens can become overheavy for their habitat and may finally be toppled over by a storm. This calls for timely decisions, as they may inflict considerable damage in their immediate vicinity should this happen. These problems are far less likely to occur on soils with lower water-tables. Felling such trees is never easy on the manager; it often means having to say goodbye to beautiful old specimens, clad in mosses and lichens. It may sometimes be possible to remove a number of heavy main branches or to cut it back rigorously. In doing so one will choose shapes that may be artificial but still fit the atmosphere of the park.
Thinning and cutting back woodland trees and shrubs will remain necessary in order to keep sufficient gaps in the upper layer, providing enough light for the lower levels to grow in. This is a neverending work, in keeping with the dynamic character of naturalistic plantings. That is why it is fiction to claim that it would be possible to reach a proper ‘final image’ by performing only a limited number of pruning rounds—six to seven times is sometimes mentioned. This is merely a forestry concept, based upon a permanent, static image only. Our parks and public gardens, with their limited scale, pose a problem in as far as one cannot go on thinning endlessly. This means one sometimes has to revert to artificial interventions, such as thinning the boles of hornbeam or field maple at a high level. This can be done in such a way that its effect is hardly noticeable from the ground level. Pruning trees in old parks has a similar workload to that of young and middle-aged parks. Although the total number of individuals to be thinned out or cut back decreases with age, the mass, girth and weight of the produced wood become greater, with the workload staying more or less equal. In naturalistic parks, as in other vegetations with high natural values, one notices as they get on in age how difficult it is to let plants do their own work as the scale of ‘nature’ in and around towns is so restricted. It is the knowledge and art of the manager that
(a) Mass flowering of Wood Anemones (Anemone nemoralis) in April.
(b) Summer Snowflake (Lencojum aestium) beneath birch trees.
(c) Flowering woodland edge herbaceous layer alongside a path.
(d) A wetland ‘meadow’ with Marsh Marigold (Caltha Palustris) and Primrose (Primula vulgaris)
allow him to exert his influence on the images and values, using larger or smaller interventions to compensate as best he can for the shortcomings caused by its small scale. He will primarily be led by the intended functions, such as the values for flora and fauna and its importance to the inhabitants, but especially by the continuity of achieving these goals.