There are an estimated 500 tree avenues on National Trust land stretching hundreds of miles which were historically planted to frame a particular view and are also now an important habitat for fungi, beetles, bats and lichens and forming natural wildlife corridors in the countryside.
The survey is the first of its kind in the world and as a result the Trust, as the largest individual owner of tree avenues in the world, will be better able to prioritise funding for their care as well as bringing together for the first time all of the fascinating stories behind the wealth of avenues.
Brian Muelaner, National Trust Ancient Tree Advisor, said: "Tree avenues are the perfect example of man and nature working in harmony. This new survey will give us the opportunity to understand more about these spectacular natural monuments which are rooted in the history of the places they appear.
"Historic tree avenues were great vanity projects for many wealthy landowners and there are some fantastic stories behind those in our care, so it's especially important that we capture all of this information in order to keep telling these stories for generations to come.
"Many of our tree avenues are under threat from different diseases so this survey will pinpoint where the issues are and help us decide how we can address them. We have an extensive tree safety management programme which assesses the risk of individual trees but avenues as a whole are not currently taken into consideration."
With more than 25,000 hectares of woodland, 200,000 hectares of farmland and 135 landscape and deer parks in National Trust care, more than 20,000 individual trees, equivalent to the size of 500 football pitches, are expected to be surveyed over the duration of the project.
Notable examples of tree avenues at Trust places include the Spanish Chestnuts at Croft Castle in Herefordshire, planted using the seeds from the Spanish Armada wrecks in 1592; the 731 trees in the Beech Avenue of the Kingston Lacy Estate in Dorset, which were an extravagant gift from Dorset aristocrat William John Bankes to his mother Frances and the Lime Tree Avenue at Clumber Park in Nottinghamshire. This is the longest such avenue in Europe with 1,296 trees (2 miles) planted in a double row on each side by the 4th Duke of Newcastle.
Brian Muelaner pointed out: "A tree avenue is a natural picture frame and there is nothing quite like walking along one as a magnificent building or spectacular landscape comes into view and the image is captured in your mind's eye."
Two years ago the National Trust launched a project to survey all the ancient trees in its care. Almost half of the Trust's properties have staff trained in surveying and 20,000 trees have so far been recorded.
The work of the Ancient Tree Advisor and the survey of tree avenues on National Trust land has been made possible with the support of Cadbury.