Common Buckthorn

Common Buckthorn (Rhamnus cathartica) The berries indicate this is a female plant. – June 2024

Common Buckthorn is a shrub or small tree, native to Europe and invasive across much of North America. It has few if any pests, tolerates shade and sunny locations and can grow well in most soils. It also alters the nitrogen in the soil which inhibits the growth of neighbouring plants. All these add up to a remarkable ability to out compete our native trees, shrubs and other plants. This has allowed it to create monocultures of buckthorn and reduce biodiversity. Bees and other pollinators that depend on our native plants, will not survive in such areas. The Buckthorn Forest starting at the Pollinator Garden and walking eastward along the chipped wood path, is a good example of this type of monoculture.

Buckthorn removal

Buckthorn can be eliminated by cutting it down and removing the roots. If the roots are very extensive, they can be killed by covering the stump with heavy black plastic or similar material for at least two years. Another way to control buckthorn is called critical cutting. Cut the plant at a convenient height (say 4 feet) and remove all the branches. When sprouts grow, remove these every few weeks or months. Eventually the nourishment in the roots will be depleted and the tree will die, but it may take 4 years or more. If any seeds have fallen, they can germinate for up to 2 years. Every few weeks, remove any tiny buckthorn trees that have sprouted in the soil in the adjacent area.

Further information

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Dog Strangling Vine

Dog Strangling Vine flowers and pods in early July 2024

Also known as European swallow-wort, Dog Strangling Vine (DSV) has populated extensive tracts of land in Riverview Park. It doesn’t actually strangle dogs but you can certainly trip on the vines. These photos were taken near the Riverview Park Pollinator Garden.

The ripe pods look a lot like those of the Common Milkweed plant and confuse the Monarch Butterfly. DSV is useless to these butterflies.  Caterpillars hatched on DSV plants die because they don’t have the food they need.

Two species of milkweed that can be planted instead are Swamp Milkweed (Asclepias incarnata) and Butterfly Weed (Asclepias tuberosa). Swamp Milkweed likes full sun but will grow well in damp, clay soil (perfect for Riverview Park!). Butterfly Weed, on the other hand, also likes full sun but does well in dryer soils.

Dog Strangling Vine removal

It is best to remove the plants before they go to seed. If you have a handful of plants, DSV can be dug up, making sure to get all the roots. Place the plants in a plastic bag to solarize (kill them!) for a couple weeks before putting them out for garbage collection. Don’t put them in your compost or in the green bin.

If the DSV is well established, it can form a dense monoculture with a thick mat of roots that are very difficult to remove, especially without breaking off bits of root that can generate new plants (kind of like the Disney movie Fantasia). In this case, to kill the plants, cut off the tops of the plants (sometimes mowing the patch works well) and then cover the area with black plastic or something that will prevent light from reaching the plants. Be sure to secure the covering, such as with rocks or something that will prevent wind or animals from disturbing it.

Further information