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S. (Willow) Stems at Bluestem Nursery

Salix (Willow)

Willow Invasiveness

Why Blame Willows?

Salix udensis 'Sekka' - a perfectly well-behaved willow

People often make reference to the invasive nature of willows. It has been said that they can destroy water pipes, clog drainage fields and septic tanks, crumble the foundations of homes, and that they are prone to blow over in storms. If these factors are not bad enough, willows are also messy with catkins dropping in the spring and leaves falling in the autumn.

While it is true that some vigorous growing willows can do some of these things, is all of this blame on willows really warranted? For instance, with regard to their falling over in storms, willows, with their quick-growing roots, are actually less likely to blow over compared to many of the shallow rooted trees. A good example is Blue Spruce (found on many suburban lots) which have a much higher risk for windthrow.

As to the notion of destroyed pipes and foundations, if pipes are leaking and foundations have cracks, willow roots will take advantage of these available resources. However, the same could be said for many other large trees and shrubs. Willow roots cannot drill holes in pipes nor damage solid foundations.

Whenever there is some uncertainty, especially around older homes and exterior plumbing, it is prudent to be cautious when planting willows. Also, it is wise not to plant any water-loving trees on or near septic tanks and drainage fields.

Salix nakamurana var yezoalpina
Salix nakamurana var yezoalpina - an alpine willow that remains low to the ground

Keep in mind that the genus Salix is a large and diverse plant group with nearly 500 species. Only a few are responsible for their bad reputation. Unless the area can accomodate large trees, avoid using Salix alba (White willow), Salix fragilis (Crack willow), Salix babylonica (Weeping willow), Salix nigra (Black willow) and the others that become large shrubs.

Coppicing (pruning back to the ground each year) will keep the roots of the large and medium willows in check. With less top growth providing energy to the roots, the root size is correspondingly less. City gardeners can enjoy many of the brightly coloured basketry willows by giving them this annual pruning.

It is certain that as willows become more popular and well-known, many more of the small and alpine types will become available.