If you have not shared your family tree with anyone then deleting it from your account page will effectively do that. You still can undelete it, but you're the only one who has access to it, so it doesn't really matter.
If you have shared the family tree with anyone (with or without edit rights), the only way to delete it is to delete all of the people from the tree. If they have downloaded the family tree, then could upload it as a seperate tree.
