The term “invasive plants” brings to mind a small army of green shoots, marching towards the forest to wreak havoc, a la Fern Gully.
If that’s what you think of, you’re not all that far off. Invasive plants are one of the harder aspects of human influence on the world to see, since they’re not all terrifying parasitic plants. If you’re not familiar with the local flowers and trees in your area, it’s hard to know whether that plant is an invasive Japanese knotweed or an innocuous native plant.
But once you get familiar with some invasive species in your area, it’s hard to ignore how many plants around the world aren’t supposed to be there.
Humans Move Invasive Plants Around the World
Invasive plants are mostly carried by humans, either as garden plants or as accidental seeds when humans move around the world. Someone may plant a flower in their garden, a dog gets a burr stuck in its fur, or you may walk through some seeded dirt and bring those seeds to a new area.
For example, purple loosestrife is a beautiful purple marsh plant that’s common in Wisconsin. It is a popular garden plant and a terribly successful invasive species. It easily escapes from gardens and takes over delicate marshlands. It’s beautiful, but it’s quite harmful.
Not all non-native plants are invasive. To be an invasive species, a plant (or animal) must be able to survive and thrive in its new environment. Invasive species generally outcompete native plants with relative ease.
In contrast, most non-native plants are simply that: non-native. Your rose bushes and your neighbor’s ornamental Japanese Oak are unlikely to spread from your lawns. They’re simply not aggressive enough or well-suited enough to the environment to take over.
So, What Makes a Species Invasive?
If not all species that aren’t native are invasive, then what is an invasive plant? As hinted at above, invasive species tend to be extremely hardy and fast-spreading. There are several specific traits that make a plant well-suited to being an invasive species:
- Lots of seeds. To succeed as an invasive plant, a plant must be able to reproduce quickly and aggressively. That’s why we don’t actually see many invasive trees – grasses tend to be the king of invasion.
- Few natural predators. Non-native plants that the native animals find tasty don’t generally become invasive. Their populations can be controlled more easily, so they’re not as dangerous.
- Difficult to kill. Many invasive plants are able to reproduce and regrow in a variety of ways. They might survive fire, uprooting, chopping, or even poison! This tenacity makes invasive species extra-dangerous.
- Many invasive species can grow a whole new plant from each broken root, meaning that pulling up the plant by its roots improperly can actually lead to the creation of more plants! Yikes!
- Tend to do well in a variety of disturbed areas. Many invasive species capitalize on disturbed ecosystems, taking root when other plants are struggling. They also tend to do well in a variety of ecosystems, rather than having a single narrow niche.
In fact, most invasive species are simply too good at “survival of the fittest.” They outcompete their native neighbors, destroying the ecosystem as a whole. In some cases, like the drought-resistant flowers of California, the native plants can still have an edge – but that’s not the norm.
Invasive Plants Hurt Native Species
If invasive plants are the powerhouses of the natural world, totally beating out the competition in the survival of the fittest, why are they so bad?
The main reason we don’t like invasive plants is that they hurt the native plants and animals of the area.
If a single, highly aggressive invasive plant takes over an area, that can really disrupt the ecosystem. Invasive plants outcompete native plants, which may be medicinal or sacred. In turn, that may hurt the pollinators in an area that depend on a specific early-flowering plant or hurt a mammal that depends on the roots of a plant for winter food.
In short, invasive plants disrupt the delicate balance that evolution built in a given area.
How Can I Help?
One of the biggest ways to help reduce the spread of invasive plants is to volunteer with trail crews. There are often trail crews that will help you learn to identify and remove invasive species in local open spaces.
You can also ensure that you familiarize yourself with the flowers and trees of your area so that you can spot one that seems off. You can then get in touch with local botanists to see what they have to say about the matter.
Finally, ensure that you use boot brushes and other cleaning devices when available. These will help ensure that you don’t track the seeds of an invasive species from one area to another!