Read what our conservation scientist in Michigan has to say about the problem, and when you're done reading, send us your questions on any conservation subject for one of the Conservancy's 720 staff scientists. (Note: We regret that we can only answer one or two questions each month and that we cannot answer the others offline.)
Jeff White of Saginaw, MI, asks:
“So much freshwater shoreline and ditches around Michigan's Saginaw Bay are choked with 11-foot-high pampas grass, yet I see new residences are still deliberately planting this invader species. My question is: Isn't there a system in place to prevent nurseries from selling invader species?"
There are federally listed noxious species, which nurseries can't sell. In Michigan, the Legislature passed aquatic invasive species legislation in 2005 that includes a list of regulated and restricted species that nurseries in Michigan can't sell — but the list is pretty short.
Since the initial passage of this legislation, the Michigan Department of Natural Resources (DNR) has developed a process for adding species to the list of prohibited and restricted species. This process involves completion of a nomination packet and submission to the DNR for an extensive review. I think that the current effort to remove yellow-flag iris from the list is the first test of this process.
At the national level, The Nature Conservancy is working with many other partner organizations and agencies to develop and enact a screening process to review non-native plant species before they are introduced to market. Any species found likely to be invasive would be prohibited by this process. Other states, such as New Hampshire, have strong legislation in place, but most states do not.
More Than One Approach to Stopping Invasive Plants
Another approach to reducing the spread or introduction of invasive species through nurseries is to adopt voluntary codes of conduct.
The Michigan Invasive Plant Council does not have a code of conduct, but green industry professionals, invasive plant councils, natural area managers and conservation organizations developed voluntary codes of conduct at a conference at the Missouri Botanical Garden in 2002. Different codes of conduct — all voluntary and non-binding — were developed for nursery professionals, governments, and the gardening public.
The Michigan Nursery and Landscape Association has formally adopted the codes of conduct for nursery professionals, which is a good first step in reducing the spread and introduction of invasive species through nurseries.
The main challenge with this approach is getting agreement on what species are invasive. Some species are obviously invasive and usually not controversial, whereas others are less obviously invasive and nurseries are reluctant to reduce sales of species without good evidence of invasiveness.
Yet another approach is to work directly with plant retailers to encourage customers to purchase non-invasive plants. Our partnership with Meijer stores is a good example of this kind of approach. The Nature Conservancy has developed a list of recommended non-invasive plants, all of which carry distinctive labels in Meijer garden centers.
About That Pampas Grass …
Pampas grass (Cortaderia spp.) is currently sold on the market and you are correct — it is being planted (legally) in many new developments. Though some species of pampas grass are considered invasive in other states, such as California, they have not become invasive in Michigan yet — it is a plant that we should watch closely.
However, the invasive plant you are seeing in wetlands is not pampas grass but phragmites, which is similar to pampas grass in appearance. Phragmites is a very tall grass that has become a dominant invader in many wetlands in southern Michigan, especially coastal marshes in Lake Erie and Saginaw Bay. It is also widespread in roadside ditches in this region.
A very helpful summary of phragmites has been completed by the MSU Extension, Michigan Natural Features Inventory. But if you are truly seeing pampas grass invading wetlands, then please report this to Phyllis Higman at the Natural Features Inventory (email: firstname.lastname@example.org).
Phragmites is not sold by nurseries as it is currently a "restricted" species (not a "prohibited" species) in Michigan. There are several fines related to restricted species, the most relevant being: "A person who sells or offers to sell a restricted species is subject to a civil fine of not less than $1,000 and not more than $10,000."
About the Conservationist
Doug Pearsall, a Nature Conservancy senior conservation scientist in Michigan.