Weeping Willow Tree

Q: Does the root ball of a Salix Babylon willow grow large? How Deep? How wide?

A: As a rule of thumb, the root system of a tree will extend to the width of its crown, so if the crown spread is a 20' radius, the roots will be at least the far. Often, the roots spread twice as wide (on some trees even 3 times) if there's nothing to impede their growth, such as a house foundation or road.

This particular variety of willow typically does not get quite as large as the regular willow (but it's close), and its root system would be proportionately smaller. The "advertised" height is anywhere from 45-70', and its spread about the same so you can see it's quite variable.

Typically, the growing conditions will have a large impact in dictating how large the tree might ultimately become -- the better the conditions, the larger it should get.

I would not plant this tree too close to any infrastructure that might be damaged by its root system. Willows are typically shallow-rooted, especially so if your soil is clayey. They do best away from buildings and other structures, preferable near a moist area such as a pond.

Anywhere too close to "civilization", and you might have a root problem some day. This is not to say you cannot plant them near something, you just need to be aware of their ever-reaching roots.

As for depth, much depends on the type of soil. Clay soils will produce shallow root systems, sandy soils will allow roots to get deeper because there's enough oxygen and water down deep for them to find as they grow. In a heavy clay soil you may find roots anywhere 3-5' down.

Base your decision in part on the type of soil you're dealing with, as well as available "air space" above ground.