Dhaka: The United Kingdom’s oldest tree Fortingall yew, located in Perthshire, Scotland is thought to be between 2,000 to 5,000 years old, making it older than Stonehenge.

Fortingall yew has long been identified as a male tree as opposed to female yews which bear red seed-holding berries.

However, botanists were shocked when ‘three ripe red berries’ were spotted on one of the branches this year, suggesting at least part of the tree had become female, reported the Independent recently.

Royal Botanic Garden of Edinburgh wrote in a blog post last month: ‘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 seperate 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.’

As many as of 17 species of cycads, a primitive group of tropical plants, can change sex. Yews are one of them including poplars, persimmons and ginkgos, writes Peter Thomas homas in his book Trees: Their Natural History.

It is said that ‘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’.