The fruit on buckthorn act as a laxative, so animals that eat it spread the seeds quickly.
Common buckthorn, from the Ontario Invasive Plant Council’s Best Management Practices Series.
Freyja Forsyth photo
There was a time when land managers promoted the planting of European buckthorn, rhamnus cathartica, along roadsides and in the windrows between fields.
The shrubby tree could reach a height of up to seven metres, was fast growing, and could survive in a wide range of habitats. It was shade-tolerant, drought-tolerant, and produced an abundant supply of fruit for wildlife. It seemed like the perfect choice.
But those were the days before environmental awareness, before it became apparent that introduced species like buckthorn, freed from competitive constraints and the insect predators of their native lands, could out-compete native species here, and become invasive.
As Paul Cottenden, forest technician with the Lake Simcoe Region Conservation Authority noted, “It takes time for us to learn some of its negative impacts.”
Introduced by gardeners in the 1880s, and then widely used for windbreaks and erosion control, buckthorn has spread aggressively. It has invaded roadsides, riverbanks, mature forests, and farm fields, forming dense stands and reducing biodiversity.
Its abundant fruit make it easy for the fast-germinating seeds to be widely disseminated, in the droppings of birds and other animals.
The fruits have an even sneakier trick to ensure spread: They act as a laxative, causing wildlife to quickly deliver the seeds into the environment.
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