You cannot ask a tree its birthday. You can read the clues.
The Woodland Trust's Ancient Tree Inventory asks the public to help put old trees on the map, by measuring girth at 1.5 m and looking for signs of great age. Tree-ring scientists go further, matching ring patterns between trees to date each ring to a single year.
Pick a girth measured at about 1.5 m to see the Woodland Trust's rough age for an oak. The bar shows how old the tree is likely to be.
Oaks only. The Woodland Trust says other species grow at different rates and can be ancient at a younger age, except for yews. Treat every figure as an estimate.
TWO NUMBERS WORTH KNOWING
Ancient depends on the species.
When an oak becomes ancient, and when a yew does.
≈ 400 years
Age before an oak is ancient
The Ancient Tree Inventory puts it at around 400 years for an oak. An older Woodland Trust leaflet sets the line at over 300 years.
OAK · WOODLAND TRUST
≈ 900 years
Age before a yew is ancient
Yews live for around 900 years before they become ancient, and can then go on for thousands of years. The Fortingall yew is estimated at 2,000 to 3,000 years old.
YEW · WOODLAND TRUST
The Inventory notes that ageing ancient trees is difficult because their trunks are often hollow, so there is no chance of counting the rings.
FOUR STEPS TO TRY
Be a tree detective.
All you need is a soft tape measure, or a piece of string and a friend. These are the Ancient Tree Inventory's own recording tips.
Find 1.5 m
Measure at 1.5 m above ground, on the upper side of a slope, or 1.5 m up the underside of a leaning tree.
Keep the tape level
Flat against the trunk, not twisted. Measure a couple of times; do not trust the first go.
Dodge the burrs
If burrs or swellings sit at 1.5 m, find the narrowest girth below that height and note where you measured.
Note the features
Look for a hollow trunk, a reduced crown, dead antler-like branches and heart-rot fungi on the trunk.
AI-generated image, not a photograph of a real person or place.
THE OTHER CLUES
Hollows, fungi and stag's heads.
AI-generated image, not a photograph of a real person or place.
The Woodland Trust lists features to look for: a crown reduced in size and height, a large girth for the species, a hollow trunk, a stag-headed crown of dead bare branches, heart-rot fungi, cavities and pools of water, and rougher bark.
A tree counts as ancient when it is in the third and final stage of its life, old for its species, and interesting because of its great age. Yews, oaks and sweet chestnuts can live for over 1,000 years; birch and willow live shorter lives.
Questions
Questions people ask
Where should I measure a tree's girth?
At 1.5 m above ground for a single-stemmed tree, according to the Ancient Tree Inventory. On a slope, measure from the upper side; on a leaning tree, measure 1.5 m up the underside.
Can I tell a tree's age from its girth?
Roughly, for oaks. The Woodland Trust's ready reckoner gives about 75 years for a girth of 1 m 85 cm and about 433 years for 6 m 20 cm. Other species grow at different rates.
Why not just count the rings?
The Laboratory of Tree-Ring Research says ring-counting alone does not ensure accurate dating. Scientists crossdate, matching ring-width patterns across many samples to fix each ring to an exact year.
What makes a tree ancient rather than just old?
The Woodland Trust says an ancient tree is in the third or final stage of its life, old relative to others of its species, and interesting because of its great age.
What is the oldest tree in the UK?
The Woodland Trust says it is said to be the Fortingall yew in Perthshire, estimated at 2,000 to 3,000 years old, though some believe it could be 5,000.
