Over the last century, a foreign invader has been displacing native species in our urban and rural areas. Common buckthorn (Rhamnus cathartica) is an invasive shrub-like tree which grows in forests and meadows across southern Ontario. This invasive species can dominate the forest understory by quickly growing upwards shading out the native plants below it. In time it even begins to alter the very chemistry of the soil itself.

Common buckthorn was brought to Canada in the 1800s by settlers who used the tree for landscaping purposes and in hedge rows. It has since escaped and taken refuge in many different habitat types around the Credit River Watershed. Have you seen one on your property? What to look for:

  • Egg shaped leaves
  • Small thorns on the tips of the branches
  • Dark grey bark: smooth when young and rough when mature
  • Black berries from late May into the winter months
  • Can grow up to 6 m tall
  • Can tolerate many different areas, from meadows to dense forests and wetlands

The juicy, black berries of the buckthorn are a favourite snack of local birds. Later excreted, the seeds are transported to new areas. This is a main reason why common buckthorn has been so successful in Ontario.

Credit Valley Conservation (CVC) lists common buckthorn as a Category 1 Transformer Species. This means it is a top priority for control due to its ability to spread, dominate and change the type of ecosystem that currently exists in order to better suit its preferred growing conditions. Once populations of Category 1 species become high, control can become quite difficult. CVC recommends the immediate removal of common buckthorn once it is identified.

If you are interested in learning how to correctly identify and remove common buckthorn and other invasive species on your property please attend our upcoming workshop on Saturday June 2.

Controlling Invasive Plants on Your Property
A Workshop for Landowners
Watershed Learning Centre @ Terra Cotta Conservation Area
14452 Winston Churchill Blvd, Halton Hills, Ontario
June 2, 10 a.m. to 3 p.m.
Please register by Monday, May 28, by calling 905-670-1615, ext. 449, or emailing [email protected]

Hope to see you there. For more information on invasive species please visit CVC online at www.creditvalleyca.ca/invasives or contact us at 905-670-1615.

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