Broadleaved trees are typically planted as 40-60cm plants at 2.5-3.0m spacing. That gives a density of 1100 to 1600 trees per hectare. A mature wood of large trees may have a density of just 200-300 trees per hectare and still have a complete canopy of leaves. The process of selecting these final trees and eliminating their competitors is called thinning.
20 years after planting a wood may have changed hands or passed on to another generation and the original reason for planting the wood may have been forgotten. Owners of woodlands may be put off by the perceived expense and health and safety implications of felling trees. New woodland owners are often puzzled by the need to thin trees, thinking it would be much less bother to “let nature take its course”. So why should I thin young woodlands?
If the young wood was left unthinned the first trees to be crowded out would be the slower growing species such as Oak. Other trees would grow tall but spindly as they competed for the available sunlight. A few Willows might outgrow all their neighbours and develop large crowns thus shading out and killing all trees nearby. In any case the woodland owner would have no control, and any dreams that the tree planter had for the future of the wood would be unfulfilled.
Thinning a young wood allows many different options. If the wood was originally planted as an intimate mixture of 5 species (20% of each) then thinning could result in a pure wood of any one of those 5 species. More likely the wood will be thinned to favour 1 or 2 species but at the same time retaining maximum biodiversity.
Thinning also allows the form of the trees to be controlled. Foresters generally favour long straight stems, so trees with heavy low branches will be thinned. Conservationists may favour other attributes of trees and select accordingly.
Finally, thinning opens up a wood for our enjoyment. After the impenetrable thicket stage when only the pre-planned rides are accessible, a thinned wood allows easy access throughout to assess what trees are growing and so to plan the future direction of the wood. The temporary increase in light reaching the woodland floor may be an opportunity to plant some ground covering shrubs or to try introducing some native woodland flowers.
Encouragement and education alone will not persuade many woodland owners to thin their young woods correctly. What is needed is practical ways of managing young woodlands at minimal cost to the owner and to the long-term benefit of the woodland ecosystem.