The words "Invasive Species" can bring up a lot of feelings and even arguments...
"My yard, my choice!" to "Kill 'em all! ...with RoundUp!"
Different people may even have different meanings when they say it. For example, some people consider aggressive native plants to be invasive. They can spread readily by rhizomes and self seeding. Most Goldenrod species definitely need to be managed in manicured landscapes, removing flower heads before they go to seed, and dividing clumps that are encroaching into areas they aren't wanted. However Goldenrod is also an important Fall food source for pollinators.
When I use the term Invasive Species it is meant for aggressive, non-natives that disrupt natural ecosystems by out competing native species. Invasives can reproduce rapidly or sometimes have life cycle differences that give them an advantage over native species.
Most people are familiar with Bush Honeysuckle (Amur & Tartarian), one of the worst offenders across the Midwest. Its lifecycle helps it outcompete native shrubs because it keeps it leaves longer in the fall getting just a little more energy and time to grow. It forms dense, shrubby, understory colonies that eliminate native woody and herbaceous plants. The berries are not edible for people, but birds readily eat them distributing seed everywhere. Look for seedlings under trees and overhead utility wires and by fences. Initially introduced as an ornamental, its planting was even formerly encouraged along fence rows to prevent erosion and for wildlife habitat.
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| Trevor displays his honeysuckle trophy |
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I love using the stump bucket to remove invasive honeysuckle!
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Another plant widely used for erosion control along highways and in agricultural grassed waterways was
Reed Canary Grass. It lays flat and conveys water quickly, however it is hard to manage and no longer recommended by conservation agencies. Lying flat under the snow it provides little winter wildlife cover and forms dense stands that reduce biodiversity.
Japanese Barberry is another invasive species widely used as an ornamental. Tough as nails, but even sharper, these "bullet-proof plants" are often seen in new construction with Spirea and Boxwoods. Like the Honeysuckle, Barberry lifecycle allows it to leaf out in the Spring earlier than native plants shading them out. The small berries can be eaten by birds which spreads their seed. They can also spread by rhizomes and their roots can interfere with the growth of other plants.
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| Barberry is a nasty one, with painful and irritating thorns |
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| Barberry at Browns Woods in West Des Moines |
One of the most beautiful, and highly invasive, ornamental shrubs is Burning Bush or Winged Euonymus. I love the color, and we had a nice row along our home when we moved in.
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| Brilliant, but Invasive, Burning Bush |
Easily propagated, hardy and beautiful, it is a staple of the landscaping industry. I eventually removed ours with machinery, but seedlings and remaining roots continued to resprout for some time. This makes established colonies of exotic burning bush very hard to eradicate. The photos below were also taken in the Fall at Browns Woods. You can notice many of the surrounding plants are dormant, while the burning bush is just starting to change color and drop its leaves (giving it a life cycle advantage).
A US Native Burning Bush, the Eastern Wahoo, is unfortunately lesser known so most nurseries and greenhouses only carry the exotic variety.
Here's a recent episode of the Small Farm Sustainability Podcast from Iowa State University
Here is even more information on Invasive Species from ISU Extension and Outreach
We also found some bittersweet on our walk in the woods...
Use of invasive species in landscaping contributes to their spread into natural areas. Avoiding these species is the first step to help control their invasion. When it comes to invasive species, the old adage is right...
An ounce of prevention is worth a pound of cure!
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That's a pile! Invasive Honeysuckle
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