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Recognising ancient trees

How do you recognise an ancient tree?

Like people, trees grow and age at different rates depending on where they are and what happens to them during their lifetime. But here’s a rough guide to when trees start to be of interest to the Ancient Tree Hunt, based on our hug method of measurement.

The 'hug' method for measuring trees

A hug is based on the finger tip to finger tip measurement of an adult, which we take to be about 1.5m. This distance is usually almost the same as your height, and means you can measure a tree even if you forget your tape measure!

The trees below might be ancient if they measured the following:

Oak – 3 adult hugs
Beech – 2 adult hugs
Scots Pine– 1 adult hug
Rowan – one adult hug
Birch – a wrist hug
Hawthorn – an elbow hug
Cedar of Lebanon – 4 adult hugs
Field Maple - 1 adult hug
Sweet Chestnut - 4 adult hugs
Ash - 2 adult hugs

(Pollarded Trees may be smaller)

Other more technical methods of recognising ancient trees include:

Size:

For most species, girth can be a useful indicator whether a tree is ancient or not and some rules of thumb do exist. However altitude, climate, growing conditions and if the tree has been pollarded or cut in the past can affect the rate at which the tree grows and is therefore only a guide to aging a tree.

Example for an oak tree:

  • Trees with a girth of more than 4.5m or 3 hugs are potentially interesting
  • Trees with girth of more than 5m or 3.5 hugs are valuable in terms of conservation
  • Trees with a girth of more than 6m or 4 hugs are likely to be truly ancient

Age:

Without cutting down a tree and counting the annual growth rings it is difficult to age a tree and some trees are hollow so for them it is even more of a challenge. Different species of tree live for a varying number of years. A 100 year-old willow or birch tree would be ancient, but a 200 year-old beech would just be starting to become interesting, an oak tree just maturing, and a yew tree only a young tree.

Characteristics:

The more of the following characteristics* a tree has, the more likely it is to be ancient:

  • Girth is large for the tree species concerned
  • Major trunk cavities or progressive hollowing
  • Naturally forming water pools
  • Decay holes
  • Physical damage to trunk
  • Bark loss
  • Large quantities of dead wood in the canopy
  • Sap runs
  • Crevices in the bark, under branches or on the root plate, sheltered from direct rainfall
  • Fungal fruiting bodies (from heart rotting species)
  • A high number of interdependent wildlife species
  • Epiphytic plants
  • An ‘old’ look
  • High aesthetic interest, also known as the ‘wow’ factor

In addition, the tree may also have:

  • A pollard form or show indications of past management
  • A cultural/historic value
  • A prominent position in the landscape

However, some ancient trees may exhibit few of these features while young trees that have been damaged (eg by fire) may exhibit them.

* Information taken from The Veteran Trees Initiative - Veteran Trees Management Handbook For more details, please see chapter 1 (.pdf file 38K) and chapter 2 (.pdf file 340k)

Another useful publication is the Forestry Commission’s Information Note Estimating the age of large and veteran trees in Britain by John White (1998)

Ancient Trees in the landscape.Photo: Archie Miles

Hollowing. Photo: Ted Green