Britain's Oldest Tree Experiencing Sex Change

The Fortingall yew tree, found in Perthshire in Scotland and as much as 5,000 years old, may be changing sex to become female. Paul Hermans / Wikimedia Commons CC BY-SA 3.0

The United Kingdom's oldest tree is the Fortingall yew in Perthshire, central Scotland, a grand tree set behind a stone wall to keep out unscrupulous souvenir hunters who have taken parts of its wood in the past decades and centuries. Scientists estimate it to be as old as 5,000 years, although this has yet to be definitively pinned down, as scientist Max Coleman explained in a post at the Royal Botanic Garden Edinburgh. Regardless, it is for certain one of the oldest known organisms in Europe.

Yews are one of many species of trees that generally come in two sexes, known as dioecious trees. Ginkgos are a familiar example, the females of which produce smelly berries and are banned on many city streets. Throughout its life the Fortingall yew has been a male, producing spherical structures that release pollen. However, last month Coleman noticed three bright red berries on one branch of the tree, which came as quite a surprise, he writes.

In his book Trees: Their Natural History, writer Peter Thomas explains that several species of dioecious trees can change sex, in part or whole. Oftentimes, only one part of the tree will change sex. But at other times, the whole tree can change. And trees have also been known to revert back to their original sex as well, he writes. Dioecious trees can also produce "hermaphroditic" flowers that have both male and female parts.

A total of 17 species of cycads, a primitive group of tropical plants, can change sex. The phenomenon has also been witnessed in yews, poplars, persimmons and ginkgos, Thomas notes.

Sometimes, the change can be triggered by times of stress or occurs at the end of the plant's life, although more often it happens for no discernable reason.

Coleman collected the berries, which 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," he writes.