Treed is the best tree app I’ve come across. It’s basically a field guide to trees found growing naturally in the British Isles. The new version features all native species, plus most naturalised ones. There’s a very a handy key which helps narrow down identification automatically (you just have to click on leaft type, bark etc). Great stuff.
Trees included in this version:
Alder, Ash, Beech, Silver Birch, Downy Birch, Box, Purging Buckthorn, Alder Buckthorn, Blackthorn, Gean Cherry, Bird Cherry, Ornamental Cherry, Crab Apple, Wild Pear, Dogwood, Elder, Wych Elm, Smooth-Leaved Elm, White Elm, Common Hawthorn, Midland Hawthorn, Hazel, Holly, Hornbeam, Horse Chestnut, Juniper, Common Lime, Broad-Leaved Lime, Small-Leaved Lime, Field Maple, Pendunculate Oak, Sessile Oak, Scots Pine, London Plane, Black Poplar, Aspen, White Poplar, Sea Buckthorn, Rowan, Wild Service Tree, Whitebeam, Spindle, Wayfaring Tree, Guelder Rose, Sweet Chestnut, Sycamore, Walnut, Crack Willow, White Willow, Goat Willow, Osier, Bay Willow, Yew