Non-native Species

A non-native species is one that does not grow naturally in a particular ecosystem. Most often, they cause damage by spreading and pushing out native species. Non-native species are also called invasive species, exotic species, plus others. Sometimes the introduction  of a non-native species is intentional, for example Norway Maple, and sometimes unintentional, for example Chestnut Blight.

According to the Ontario Invasive Plants Council, there are over 400 invasive plant species in Ontario.

Species not native to the Carolinian Zone fall into several categories:

1. Species that grow nearby
This includes the planting of large numbers of White Spruce, Red Pine and Paper Birch from the north, and Catalpa, Black Locust, Yellow Wood, Sweet Gum etc. from the south. Some of these species do spread and take up resources from native species. A particularly bad one is Black Locust.

2. Species from Europe and Asia that are not invasive:
There are a few that are not particularly invasive, for example, Copper Beech and Horsechestnut.

3. Species from Europe and Asia that are invasive:
Norway Maple
Scots Pine
European Alder
European Birch
Autumn Olive
White Mulberry (a serious threat to the native Red Mulberry)
Crack Willow
Tree of Heaven (Ailanthus)
Austrian Pine
Norway Spruce
Weeping Willow
European Larch
European Linden
London Plane Tree (it is however is a cross between a native Sycamore tree and the Oriental Plane Tree)

Many of these species have native counterparts, but it was a misguided trend in the past to plant these species because they were hardy, pretty, trendy etc. In a foreign ecosystem, these species have no pests to control their numbers, and often produce multitudes of seeds.

There is no denying the beauty of this Copper Beech tree, a variant of European Beech with purple coloured leaves. This  species does not pose a threat due to the nature of its growth habits. Copper Beech is a slow grower, this specimen being about 100 years old.

On the other hand, it was known back in the 1800s that Tree of Heaven was undesirable with its rapid, spreading growth. The northern part of Rondeau Provincial Park is over-run with Tree of Heaven.

There are many beautiful native species, so why choose an invasive???