Willows can have roots above ground so I would steer clear of them. I have an ornamental crabapple which gives me no problem with roots and a very tall blue spruce. No problem with roots with the spruce but it does suck up any moisture that the daylilies need. I don't have any daylilies planted directly under the spruce but at least 4 to 5 feet away but they still suffer from moisture loss from the spruce. I have daylilies planted under the crabapple and they only get a half a days sun and they bloom just fine.
