
I understood that willow trees were one of the worst trees to have near a house as they require so much water (which is why they are often found on river banks)
Pretty sure Lea will be along soon to say whether or not I am right or wrong though :)
I did find this though ..which gives types of trees and the distance they should be from a house
Trees it makes for good reading ;) It shows the willow should be 40 metres away (The relevant table is about half way down the page but the whole page is quite interesting)