In reply to adi bryant:
Tree Root (f4+) - At Woodwell there's a HS that back and foots between the rock and a large tree (I think it's an ash).
At Shepherd's Crag,
Jackdaw Ridge (D) has an optional back and foot tree, which comes in handy. There is also (though I've not yet climbed it) the "arborial corner" of
Brown Slabs Crack (VS 4c) - though I think the tree roots just provide pro!
At Lower Falcon Crag,
Hedera Grooves (VS 4c) involves climbing through the prickles of a stout holly, which many also use as a belay ledge. Leaving the tree is the crux!
Finally, you get extra points for climbing
Lone Tree Groove (S 4a) without using the poor tree as a handhold; whilst other, less climbed, routes at Warton involve struggling through trees (and gorse) at the top...
I always love reaching a good tree - when you're gripped out of your mind, there's nothing better than wrapping yourself around a stout one, slinging it and having a breather!