Any cattle farmer who’s tried to fix a barbed-wire fence in the far corner of the Back 40 knows willow can be an aggressive species.
Ken Van Rees, an agriforestry researcher at the University of Saskatchewan, can also attest to the tree’s vigorous growth.
This spring, Van Rees was surprised to learn that willow varieties in his agriforestry research plots near Prince Albert, Sask., recorded nearly three metres of new growth in one season.
“I was very surprised at the growth coming out of that material,” Van Rees said. “Whether it was the soils or whether it was a ground water table close to the surface, I’m not sure. But I was pleasantly surprised.”
Read Also
VIDEO: Green Lightning and Nytro Ag win sustainability innovation award
Nytro Ag Corp and Green Lightning recieved an innovation award at Ag in Motion 2025 for the Green Lightning Nitrogen Machine, which converts atmospheric nitrogen into a plant-usable form.
Van Rees, one of a handful of willow researchers on the Prairies, has been studying willow agronomy for several years.
The growth recorded at Prince Albert suggests willow holds considerable promise as a biomass energy crop.
Some hybrid willow species are able to produce as much as five tonnes of oven-dried biomass per acre in a single year.
That compares favourably with other biomass crops such as switchgrass and hemp, which can also produce four to five tonnes per acre under the right growing conditions.
On a per tonne basis, energy values are generally higher in willow than in switchgrass and hemp fibre.
Switchgrass and hemp are sown and harvested annually, while willow is normally harvested four years after planting.
To further explore the potential of willow, Van Rees and his associates have established four research plots in Saskatchewan.
The Prince Albert location was the most productive site last year.
Other plots at Birch Hills, Estevan and Saskatoon had single-year growth rates of 1.8 to 2.5 metres, depending on the willow variety.
Although willow agronomy is a relatively new field of study in Western Canada, Van Rees and other researchers believe the crop warrants further examination.
In some European countries, most notably Sweden and the United Kingdom, willow cultivation is a well-established practice.
For example, more than 37,000 acres are dedicated to willow production in Sweden, where biomass furnaces are common in many communities.
Canadian researchers use a system that gives new cuttings a year to establish and then coppices them the following spring to encourage the emergence of multiple shoots.
Trees are normally coppiced a centimetre or two above the ground level and then allowed to grow for three more seasons before they are harvested.
When cultivated as a biomass crop, willow is normally planted in a double-rowed format, with rows 60 centimetres apart and cuttings placed at 60 cm intervals within each row.
In good soil, the crop can be planted at a density of roughly 6,000 stems per acre.
After it is harvested, the dried biomass can be chipped and incinerated, pelletized, converted to gas or used as a feedstock for cellulose ethanol production.
Specialized planting and harvesting equipment isn’t readily available in Canada, making establishment and production costs relatively high and limiting markets for harvested material.
“Right now, the establishment costs are phenomenal because of the amount of material that has to go in the ground,” Van Rees said.
Establishment costs in Canada can easily exceed $2,000 per acre.
Bill Schroeder, agriforestry research manager at Agriculture Canada’s Indian Head Shelterbelt Centre near Indian Head, Sask., said willow varieties can also play a critical role in maintaining the health of sensitive riparian areas and water resources.
Native species are well-adapted to Canada’s harsh growing conditions and are adept at intercepting unused agricultural nutrients such as nitrogen and phosphorus.
“We see a huge opportunity for the use of willows because of their high nutrient uptake and their high water use, as a means of intercepting nutrients as they’re making their way from agricultural lands to wetlands or other types of water bodies,” he said.
Schroeder said a willow breeding program at the shelterbelt centre is developing hybrid willow lines that combine high growth potential with good winter hardiness.
The breeding program began three years ago and encompasses 25 hybrid willow varieties with roughly 150 genotypes in each variety.
Schroeder said wide variations between genotypes should allow breeders to breed new genotypes with enhanced vigour.
“I would suspect from the breeding work that we’re doing right now, our goal would be to increase productivity by at least 20 percent.”
Schroeder said producers who want to establish their own shrub varieties can do so by taking cuttings from existing native varieties on their land.
For best results, cuttings should be taken in early spring before budding occurs.
Cuttings should be about 25 cm long and 10 millimetres in diameter and should be taken from new plant growth that occurred during the previous year.
The cuttings should be placed in well-tilled soil as soon as possible after the ground has thawed. The top of the cutting should be flush with the soil surface, with no more than one or two cm exposed.
Soil moisture should be monitored closely and weeds and other competitors should be eliminated.
The cuttings will normally be well-rooted after one growing season.
Through its Prairie Shelterbelt Program, Agriculture Canada’s agri-environment services branch already offers two tree willow varieties that have an upright growth habit and are well suited for windbreaks.
In a few years, native shrub varieties such as pussywillow and heartleaf willow may be offered to farmers and landowners who are concerned about habitat conservation and riparian area management, Schroeder said.
