in a similar sense to fauna, and for similar reasons, the flora is impoverished compared to that of continental europe. the flora comprises 3,354 vascular plant species, of which 2,297 are native and 1,057 have been introduced. the island has a wide variety of trees, including native species of birch, beech, ash, hawthorn, elm, oak, yew, pine, cherry and apple. other trees have been naturalised, introduced especially from other parts of europe (particularly norway) and north america. introduced trees include several varieties of pine, chestnut, maple, spruce, sycamore and fir, as well as cherry plum and pear trees. the tallest species are the douglas firs; two specimens have been recorded measuring 65 metres or 212 feet. the fortingall yew in perthshire is the oldest tree in europe.