The term invasive species refers to a subset of introduced species or non-indigenous species that are rapidly expanding outside of their native range. Invasive species can alter ecological relationships among native species and can affect ecosystem function and human health. A species is regarded as invasive if it:
- has been introduced by human action to a location where it did not previously occur naturally,
- becomes capable of establishing a breeding population in the new location without further intervention by humans, and
- spreads widely throughout the new location.
In simple terms, an invader has to (1) arrive, (2) survive, and (3) thrive.
With regard to invasive plants, introduced species can become invasive for many reasons including:
- the insects, fungi, mammals or other fauna that kept the species in check within its native landscape do not exist in the region to which the species was introduced.
- the species is allelopathic (exudes chemicals which inhibit growth). Some species release chemicals which directly inhibit the growth of other plants, while others may release chemicals that negatively impact mycorrhizal fungi.
- the invasive species has a competitive advantage such as earlier leaf-out, asexual production, deeper root system, etc.
Please be on the lookout for the following species in your home landscapes and also in natural areas you visit. The following are some of the most common and widespread invasive plant species in Michigan and the Great Lakes Region. WAM encourages you to remove these species from your home landscape when identified. If you see these species in your local nature preserves, parks, or public lands, please contact the steward or organization that manages the site and let them know where the invasive population was seen.
- Garlic Mustard (Alliaria petiolata)
- Autumn Olive (Elaeagnus umbellata) & Russian Olive (Elaeagnus angustifolia)
- Common Buckthorn (Rhamnus cathartica) & Glossy Buckthorn (Rhamnus frangula)
- Purple Loosestrife (Lythrum salicaria)
- Spotted Knapweed (Centaurea maculosa or Centaurea biebersteinii)
- Exotic Bush Honeysuckles - Lonicera fragrantissima (fragrant honeysuckle), L. maackii (Amur honeysuckle), L. morrowii (Morrow's honeysuckle), L. standishii (Standish's honeysuckle), L. tatarica (Tartarian honeysuckle), L. xylosteum (European fly honeysuckle), L. X bella (hybrid, pretty honeysuckle) and possibly others
- Common Reed (Phragmites australis)
- Multiflora Rose (Rosa multiflora)
- Japanese Knotweed (Polygonum cuspidatum)
- Black Locust (Robinia pseudoacacia)
- Oriental Bittersweet (Celastrus orbiculatus) - please note, it can be difficult to distinguish between this species, our native species (Celastrus scandens), and hybrids between these
- Japanese Honeysuckle (Lonicera japonica)
For a more thorough discussion on the background, impact, identification, and control of invasive plant species, we suggest following the links below: