Invasive Plant Species

Invasive plants are plants that are not native to a specific area, and tend to take over. They tend not to have any habitat value for native animal species. Some non-native plant species do not become invasive, but some can become a real problem, such as the Himalayan blackberry. As a kid, I didn’t know it was not native because it grew everywhere. Now, I understand how invasive and what a problem it has become. This plant reproduces easily both be seed and by vegetative growth. Don’t get me wrong they have delicious berries for both us and other animals, and bees love its flowers, but it takes over. It out competes most of the smaller native plants and shades them out. Even trees can be overcome by them. Also, people may think it is good habitat for birds and small mammals but it is not. It works for a few, like the Junco because it nests on the ground and for rabbits to hide in. Most birds cannot use it for shelter because of the thorns that can injure them, and it is very dense. The Himalayan blackberry can grow to become a monocrop leaving no diversity of native plants that our native animal species depend on. English Ivy is another invasive plant that completely takes over smothering out native plants and can even kill trees by climbing up the tree and growing roots into the tree, and literally sucking the life out of the tree.

Another is the Japanese Knotweed, it is a perennial plant that can grow to a height of 10 feet (3m) and spreads vegetatively by underground stems (rhizomes) and if pieces of the rhizomes are left in the ground they will regrow. So, extremely hard to get rid of. It is a pretty bush that the bees love, but it will take over. We have many beautiful native plants that provide for our native animal species, as well as many non-invasive plants that are pollinator friendly. See the categories on the right menu for plants that might work for what you want, and learn about some of the animal species they support.

Scotch Broom (Cytisus scoparius) is another invasive plant because it produces tons of seed that are viable for up to eighty years. So once the plant has produced flowers that have gone to seed and dispersed it will be hard to get rid of.

Yellow Archangel is a perennial plant that is used in hanging baskets as a trailing filler plant. When some people throw out the contents of their old hanging basket into natural areas or plant it thinking it’s a nice plant they don’t realize how invasive it is. It will quickly take over choking out many native plants. Periwinkle is also sold in garden stores as a pretty evergreen ground cover, which it does really well, but again in natural areas it quickly take over. English Ivy, Yellow Archangel, and Common Periwinkle used as ground covers do not have any habitat value and outcompete many native plants that do provide habitat value. For example, the native violets are host plants for fritillary butterflies.

English Holy is a great plant for Christmas decoration with its gloss green leaves and red berries, but the red berries are eaten by birds and dispersed. It grows in sun and shade becoming more invasive as more plants get established. The butterfly bush (Buddleja davidii) as well, produces many flowers which then produces tens of thousands of seeds that are dispersed by wind and water.

For more information on invasive plants and animals, check out the Invasive Species Council of British Columbia.