The Fortingall Yew in Perthshire is a tree of international renown as potentially the oldest individual tree in Europe. It has been suggested that it could be as much as 5,000 years old, but this is not universally accepted and needs some qualification. For a start this is an estimate based on a girth measurement of 56 feet by Thomas Pennent in 1769. In old yews the definitive evidence in the form of annual growth rings has long since rotted away. The word ‘individual’ becomes important in qualifying this assertion as we now know certain trees clone themselves and can greatly exceed 5,000 years. Nevertheless, it is still a remarkable thought that this invidual yew tree could have been growing before the Great Pyramid of Giza or Stonehenge were even begun.
The first thing visitors notice about this ancient tree is that it is surrounded by a small enclosure built of stone with sections of iron railings giving glimpses of the ancient hulk within. The whole experience is reminiscent of a trip to the zoo. This unfortunate state of affairs came about as a way of putting off unscrupulous souvenir hunters who would help themselves to parts of the tree.
Closer examination reveales the Fortingall Yew is a male tree. Yews are normally either male or female and in autumn and winter sexing yews is generally easy. Males have small spherical structures that release clouds of pollen when they mature. Females hold bright red berries from autumn into winter. It was, therefore, quite a surprise to me to find a group of three ripe red berries on the Fortingal yew this October when the rest of the tree was clearly male. Odd as it may seem, yews, and many other conifers that have separate sexes, have been observed to switch sex. Normally this switch occurs on part of the crown rather than the entire tree changing sex. In the Fortingall Yew it seems that one small branch in the outer part of the crown has switched and now behaves as female.
Three seeds have been collected and will be included in an ambitious project to conserve the genetic diversity of yew trees across their geographic range including Europe, the Caucasus, Western Asia and North Africa. The project will see the exisitng perimeter hedges at the Botanics replaced by a conservation yew hedge grown from cuttings and seed collections made from wild populations and significant ancient trees like the Fortingall Yew. The first phases of planting went in the ground in 2014 and on completion the hedge will encircle the Garden with a remarkable genetic resource of over 2,000 individual trees, each of which will have a story and can be traced back to their origins in Britain or beyond. This hedge could well be the largest conservation hedge of its kind anywhere in the world.
As it matures the hedge will display a range of characteristics reflecting the genetic diversity of the many individual trees involved and as such it will not look like any existing yew hedge. The Fortingall Yew itself will be represented in the hedge and so too, all being well, will its offspring via the curious ability of yew trees to change sex.