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invasive vs non-native

Invasive or Non-native? What’s the difference?

Invasive plant species have been a hot topic in recent months. Everything from wild mustard to milfoil. But it wasn’t until I was at a city commission meeting with my daughter a few months ago that I realized that non-native seems to have become synonymous with invasive: there was some construction work that needed to be done and the contractor was wanting to have 60 year old Chinese Elm trees removed citing them as invasive.

As I was watching these city commissioners nod their heads in agreement while discussing the removal of these big beautiful trees I realized than many if not all of the commissioners weren’t aware of the difference between invasive plants and non-native plants.

So what is the difference between invasive plant species and non-native plant species? According to the Michigan Invasive Species home page, “An invasive species is one that is not native and whose introduction causes harm, or is likely to cause harm to Michigan’s economy, environment, or human health.”

The key words here are “causes harm.”

In Michigan, an invasive species that is getting a lot of attention right now is garlic mustard (Alliaria petiolate). Garlic mustard thrives in wooded areas and can tolerate deep shade, partly because it emerges and blooms before trees develop leaves in the spring. It’s choking out the native plants causing harm to the ecosystem.

Another invasive that’s getting a lot of attention is giant hogweed (Heracleum mantegazzianum). The sap of the giant hogweed can cause a severe skin reaction that can cause the skin to blister when exposed to the sun. This invasive plant causes harm to humans.

Both of these plants are invasive.

However, let’s look at a well-known landscape plant – the hosta. Hostas are native to Asia. They have become a very popular plant for shaded plantings. They are non-native, but not invasive. Another example is purple coneflower (Echinacea purpurea) which is a popular plant for sunny locations and even has some medicinal properties. And while both of these examples are spreaders, they are not invaders as they cause no harm to surrounding ecosystems.

The short version is to remember that non-native does not equal invasive, select plants for the landscape that are best suited to each planting site, and consult your state’s invasive plant species list before planting.

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