This season, we are zooming in on plants that are beneficial to our area and plants that aren’t! Ready to learn about invasive species? Let’s go.
What is an Invasive Plant?
A plant is considered invasive if it is not native to the environment it’s growing in, spreads aggressively, and causes damage to its ecosystem.
Plants are supposed to be kept in check by their environments. For example, local wildlife munches on certain plants, keeping their growth rate in a range that makes sense for all the other organisms it’s interacting with. If a plant doesn’t fit into the natural system of checks and balances, then it can grow uncontrollably and take over large swaths of land. It crowds out native species and can’t feed the local critters because they are used to feeding on native species.
Though native plants have all kinds of innate knowledge to survive their environments, they aren’t fit to compete for space. Invasive plants’ roots can be more aggressive or grow taller than natives, blocking them from the sun. They gradually change the microclimate of any given area and the native species are forced to give up. It’s a domino effect.
An example of a popular plant in our area that is invasive is the Bradford Pear (Pryus calleryana). This early spring bloomer, pictured below, produces full, bright, white blossoms. We often see Bradford Pear branches held together by cables. This is because it has a narrow branching structure that makes it weak.
The Bradford pear was originally introduced to North America from China and is now one of the most detrimental plants in this area. Many landscapers and homeowners choose this plant to herald spring, but it’s plain to see that the risks outweigh the benefits. It doesn’t support as many species as a native would, so our local populations are lacking food and habitat. By planting this tree where it doesn’t belong, we are creating an imbalance in our ecosystem; a hole that a keystone species could easily fill (learn about keystone species in our blog!). It is important to choose plant material that gives to its ecosystem, rather than taking away from it.
Another local plant that is beloved as well as invasive is the Japanese barberry (Berberis thunbergii). Native to Japan, it has a high ornamental value but our local birds eat the berries and spread them in wild spaces. It outcompetes native species and also lacks natural management from local wildlife; the deer won’t touch it! Though we love to incorporate exotic blooms into our landscapes, they bring imbalance to our populations.
As settlers moved over to the states, they brought many plants with them that were staples in their diets and lifestyles. Many medicinal herbs from Europe have since become invasive, like spotted knapweed (Centaurea stoebe) and purple loosestrife (Lythrum salicaria).
Garlic mustard (Alliaria petiolata) was one that was brought to the US for its herbal and medicinal qualities, and for erosion control. You’ll probably recognize it in the photo below. During its time here, it has escaped cultivation and intentional plantings and is becoming a hindrance to our natives. While the natives are trying to reproduce and continue thriving in their native environment, garlic mustard blocks their sunlight and outcompetes them for moisture and vital nutrients. It is edible, so feel free to go harvest as much as you can eat!
As gardeners, we have a great responsibility to choose plants that nourish all the organisms that they interact with. Learn more about invasives in the Michigan area here.
Until next thyme,
My Thyme Gardens