Willow Propagation
The value of diverse seed propagation of willow species

Richard T. Haard, Ph. D.
Plant Propagation Manager
Fourth Corner Nurseries

Every native tree and shrub that we have available for use in any planting is part of a "tool-kit" used to make a viable plant community. We know that many native species have very specific requirements for soils, moisture availability, shade, etc., and that others will thrive in a broad range of habitats.

This same range of habitat specialization seen in all the native shrubs can be found within the willows themselves. For example, different Western Washington willow species can be found in a wide range of habitats, from very dry sandy river-bars (Salix sessilifolia) to lake-shores (Salix geyeriana), upland mixed forests (Salix scouleriana) to seasonally flooded riparian areas (Salix piperi). Growth rate and ultimate stature is also quite variable, even within the same species complex. The many strains of Scouler willow vary from slow growing shrubs to a rapid growing tree.

It is the variability within the species that allows the willow to become so successful in a wide spectrum of habitats. Scouler willow (Salix scouleriana), for example, has a very wide-ranging distribution: from Manitoba to Yukon and Alaska to northern Mexico. Within a single population of Scouler willow in western Washington a pattern of variations in growth form can be observed that represents a complex species utilizing every habitat opportunity. We have determined that the different growth forms of Scouler willow are true to type from cuttings. We call them "tall," "short" and "medium."

For the past two years we have been learning how to recognize different strains of willows and making selections for inclusion in our native plant propagation program. We are moving from propagation of willows from wild cuttings collected in mixed populations to cutting orchards of seed-bed propagated strains that represent a genetic sampling of the species.

Our seed-bed-propagated willows represent an opportunity for anyone who wishes to maintain a pure strain for a cutting bed or to reintroduce a reproducing colony into the natural environment.

The Soil Conservation Service, Corvallis Plant Materials Center, has introduced a series of willow 'varieties' for restoration use in the Pacific Northwest. These plant selections, however useful, are unisexual (mostly male) clones that were screened for performance in a series of field tests. It is true that we must be careful to avoid introduction of exotic, reproducing willow strains into the local environment. The native flora has been contaminated everywhere by introductions of reproducing alien species such as Crack willow (Salix fragilis) and escaped ornamental willows such as S. alba, golden willow.

On the other hand, to eliminate the natural range of variability provided by sexual reproduction of a species and to prevent natural regeneration by seed in the riparian environment where periodic disturbance is natural is to invite failure in the long term.

Our willow propagation mission at Fourth Corner Nurseries is to offer consistently diverse seed -propagated plants of our common species, and to begin offering our other indigenous willows found in the lowlands and mountain locations as seed-bed-propagated cuttings and rooted plants.