Non-native Species

A non-native species is one that does not grow naturally in a particular ecosystem. They can be any type of living thing, from flowers to trees to fungal diseases. Some non-native species are described as "naturalized", in other words, they have been in an area for so long that they propagate on their own and can appear to be "natural". But they are NOT native.

Non-native species are often invasive and can cause damage by spreading and pushing out native species. Sometimes the introduction of a non-native species is intentional, for example Norway Maple, and sometimes unintentional, for example Chestnut Blight, which decimated the Chestnut tree population in North America.

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

In the Carolinian zone, there are several categories of non-native species.

1. Species that grow nearby:
This includes the planting of large numbers of White Spruce, Red Pine and Paper Birch from the north, and southern species such as Catalpa, Black Locust, Yellow Wood, Sweet Gum etc. Some of these are not particularly invasive, but some are. 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.


There is no denying the beauty of this Copper Beech tree, a genetic variation of European Beech with purple coloured leaves. This species does not pose a threat as it is a slow grower, and does not readily produce offspring. The above specimen is close to 100 years old. There is no native tree that has a typical colour similar to Copper Beech, although there are random genetic variations that can be found in the wild. However, these variations are not propagated and marketed. 

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

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


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

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

In fact, many of our native trees are rarer than many of the non-native ones. For example, Norway Maple is unfortunately found everywhere, but try to find Cucumber Magnolia. Tulip Tree and Sycamore (London Plane Tree) are found all through Europe but are less common in their native landscape than the Norway Maple!??!

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