First, define the word sustainable. There are lots of non-native plants that are “sustainable” right here in Michigan and they are desirable plants for many gardens, serving various useful landscape purposes. Many of these non-native plants are too sustainable, having become environmental pest plants — for instance, purple loosestrife, Norway maple, buckthorn and a host of others. Then there are the obvious native plants that don’t stand a chance for a future on this continent. The native ash tree (a common wetland tree in Michigan) would be excellent in a rain garden except for one huge problem: the emerald ash borer. This plant, alas, is no longer sustainable, though it is highly desirable.

As for pesticides, they are the only solutions in some cases. I strongly agree we need to limit pesticides and I am 100 percent in favor of all farmers and food producers who do this. I am also in favor of commercial nurseries and landscapers finding and using plant material that is less susceptible to pests and disease and more ecologically diverse. I also agree we cannot contaminate groundwater in a rain garden by using pesticides. By doing this we are required to use plants that don’t need pesticides. In the long term, this could limit the diversity of plants we use in the landscape, which we should not let happen.

As for fertilizer, all plants need nutrients. Whether we add commercial fertilizer or cow manure or the plant gets its food from its wild habitat, all plants need nutrients. Rain garden plants often have a more limited need for large amounts of fertilizer. Yet, rainwater does contain nutrients and so does runoff. Some of these nutrients are undesirable even to the most sufficient rain garden plant. Beware!

Hope Rankin

1993 MSU horticulture graduate
Botanical Technician, Beal Botanical Garden