A veteran tree or legacy tree is a tree which, because of its great age, size or condition, is of exceptional cultural, landscape or nature conservation value.
Veteran trees vary in age depending upon their species and location, but may be several hundred years old. Smaller and shorter-lived tree species (such as orchard trees) may begin to develop some veteran features when only a few decades old. Size is usually used to define veteran trees. This may be size alone: for example, a girth of over 3 metres (9 ft 10 in) at 1.5 metres (5 ft) may be used as a test; alternatively, different girths may be set for species of different sizes, and the presence of veteran tree features may also be considered.
Veteran trees often have features of particularly high nature conservation value, such as dead limbs, hollows, rot-holes, water pools, seepages, woodpecker holes, splits, loose bark, limbs reaching the ground, and epiphytic plants and lichens. Few of these features are found on younger trees, and they provide habitats for very many species of animals and fungi, some of which are rare. Such features are sometimes removed or damaged by pruning or other arboricultural practices.
Many of the oldest trees are pollards, as pollarding removes the weight and windage of the upper trunk and so reduces the chances of major damage, and it also maintains the tree in a vigorous state.
Veteran trees occur in many situations, occasionally in dense woodland, but more commonly as hedgerow trees, on village greens, and in ancient parks and other wood pasture.
Veteran trees are more frequent in Great Britain than in many other parts of Europe. In the United Kingdom in recent years, these trees are being recorded by the Ancient Tree Hunt so that a national database can be created. Volunteer groups such as the Wokingham District Veteran Tree Association, the Dorset Greenwood Tree Project and the Ashford Veteran Tree Initiative are crucial to the success of this scheme.