I am amazed how often even professional garden writers point out that willow in general is invasive – meaning spreading by sending out suckers that soon will create a thicket of unruly shrubbery.
Personally I do not have any experience with suckering willows – but again, I only have thirty some different varieties of willow here on the farm. To try to get an idea of the extend of willow species with a suckering habit, I turned to one of my favorite books when it comes to more scientific information: “WILLOWS The Genus Salix” written by Christopher Newsholme where the following information can be found:
The genus Salix belongs to the plant family Salicaceae (poplars are the same family) and comprises of some 400 species of willows and more than 200 listed hybrids, popularly known as willows, sallows and osiers. It consists of mainly deciduous trees and shrubs bearing catkins.
The genus consists of three main subgenera:
- Subgenus Salix (Amerina), the true willows
- Subgenus Caprisalix (Vetrix), the osier and sallows
- Subgenus Chamaetia, dwarf, creeping, Arctic or mountain shrubs.
Confusion and uncertainty exists in the taxonomy of this genus and although acknowledging that no method of classification below subgeneric level is entirely satisfactory, Newsholme subdivides the genus Salix into groups and sections intended as a taxonomic guide indicating which species are generally considered to be closely related.
- Subgenus Salix is divided into 3 groups and a total of 11 sections
- Subgenus Caprisalix is divided into 4 groups and a total of 14 sections
- Subgenus Chamaetia is divided into 5 groups and a total of 7 sections.
Of all these sections only one: Subgenus Salix, group 2, section Longifoliae is mentioned to produce suckers from the roots and be thicket-forming. The species in the group are:
- S. exigua – Coyote Willow
- S. fluviatilis
- S. interior – Longleaf Willow or Sand Bar Willow
- S. melanopsis
- S. sessilifolia
- S. taxilolia
- hybrids between some of the above mentioned species
These species and hybrids are native to western North America. Most of them are described as beautiful shrubs or small trees – but if you don’t want a thicket of willows, don’t plant these in your garden.
Based on this scientific information I conclude that all other species and hybrids of willows will not sucker from the roots and you can safely plant them in your garden.
For further information I refer to Newsholme’s book Willows, The Genus Salix. As I do not grow any willows with root suckering habit here, I don’t have any images to show you.