The Walnut Tree (Juglans regia)
A tall treegrowing up to 100ft (30m) tall with branching arms and a fissured bark. It's leaves are alternate with 5-9 leaflets.
The fruit is fleshy and green and around 4-5 cm. The walnut is inside in a wrinkled stone that requires cracking.
Walnuts are best picked when they are fairly dry and ripe (late Oct. - Nov.). If you want them young July is a good time to pick them whilst they're green.