We are about to purchase a house that has a 40 foot willow tree in the garden that is approximately 40 foot from the house. Is this an issue? I understand the roots of the tree may well exceed the height of the tree and we are concerned that the roots may have impacted to foundations.
Willow Tree – Proximity to a House
Certified GKH Gardening Expert
Willow trees are definitely known to have invasive roots, so your concern is valid, however there's no way of knowing how extensive the root system is without digging around it. Ideally, the tree should have been planted more like 50 feet away from the house but even then, if it doesn't affect the foundation, there's still a chance it could damage pipes. You could consider installing a root barrier, and this article may help you with that:
This article contains more information on trees with invasive roots: