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Exotic species include those plants or animals that are not native or indigenous to a specific location. It sounds simple enough, but there is more to know.
All plants have a geographic range where they occur naturally. These ranges can and do change over time. Simply put, plants move. Historically this movement was slow and constrained by many obstacles such as weather, oceans, competing plants and other habitat changes relating to soils, moisture and light. However, those factors have become more rapid and serious over time, as people have become more mobile, increasingly disruptive, less careful about their actions and more selfish about achieving personal goals. One result is that we have moved many species, intentionally or not, to new locations all around the world. In some cases exotic species find just the right niche and become highly competitive with native species already in place, reducing diversity and upsetting stable communities of both plants and animals.
Restoring native plant communities usually means excluding exotics from a site, which requires knowledge in order to identify plants that are not native.
In most situations the information is well documented, but there are degrees of “nativeness” to consider when planting and managing a restoration project. Is the plant naturalized from another part of North America. How far has it moved? Will it damage the balance of your restoration? Is it a part of the plant community you are modeling? All are important questions to consider.
A list of the exotic plants found in Minnesota or the upper Midwest would number in the hundreds. Many are relatively rare and of fairly minor concern, but others are highly problematic. A list of the worst culprits follows:
| Forbs |
| Garlic Mustard |
(Alliaria petiolata) |
| Leafy spurge |
(Euphorbia esula) |
| Sweet clover |
(Melilotus sp.) |
| Bird’s foot trefoil |
(Lotus coniculatus) |
| Crown vetch |
(Coronilla varia) |
| Spotted knapweed |
(Centaurea maculosa) |
| Canada thistle |
(Cireium arvense) |
| Bull thistle |
(Cirsium volgare) |
| Musk thistle |
(Carduus nutans) |
| Plumeless thistle |
(Carduus acanthoides) |
| Wild parsnip |
(Pastinaca sativa) |
| Queen Anne’s lace |
(Daucus carota) |
| Tansy |
(Tanacetum vulgare) |
| Grasses |
| Reed canary grass |
(Phalaris arundinacea) |
| Narrow-leaved cattails |
(Typha angustifolia) |
| Eurasiam water milfoil |
(Myriophyllum spicatum) |
| Smooth brome |
(Bromus inermis) |
| Woody Plants |
| Common buckthorn |
(Rhamnus cathartica) |
| Glossy buckthorn |
(Rhamnus frangula) |
| Tartarian honeysuckle |
(Lonicera tatarica) |
| Black locus |
(Robinia pseudoacacia) |
| Multiflora rose |
(Rosa multiflora) |
| Siberian elm |
(Ulmus pumila) |
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