"One of the greatest challenges [for trees in city environments] is just space," says Andy Hirons, a senior lecturer in Arboriculture at Myerscough College in Lancashire, pointing out that large trees in the wild have vast root structures, often sprawling out nearly as far as their branches do. But in cities, the spaces we carve out for them are "often woefully inadequate for the size of the tree and the ambition those planting the tree have for it", he says.