By Bill Brighoff
Last spring, a lawn care salesman came to my door and told me I had weeds in my yard, particularly white clover. I told him that I had planted the white clover in my yard, and how could it be a weed if I had purchased the seeds at a feed store. He left muttering that clover is a weed.
I am sure that many of us native plant growers have been accused of growing weeds. So what is a weed? Ralph Waldo Emerson is quoted as defining a weed as “a plant whose virtues have not yet been discovered”. As all of us have had to remove undesired plants from our gardens, that is probably not a working definition we would embrace. State and the Federal governments specifically list about 10 weeds each that are noxious weeds (Missouri’s list was discussed in the April 2011 St Louis Wild Ones newsletter.), but I am sure we could name more than 10 weeds in our own yards. Perhaps the most useful definition is: “a plant growing where it is not wanted”. This even covers the more aggressive of our native plants when they propagate in our, or worse, our neighbor’s yard.
I am constantly surprised when I learn of the geographic origin of plants with which I am familiar. Daisies, daylilies, and mullein were all so ubiquitous that I was sure that they were natives. And although they were also conspicuous due to there widespread distribution, ragweed, giant ragweed and smart weed had to be invasive, exotic species. I was also surprised when I looked through a wildflower book on common flowers of Door County, Wisconsin. It is easy to accept that many of the plants on the East Coast, where I grew up were “foreigners”, as the area has a long history of European immigration. However, of the plants listed in the remote land of Door county, at least 1/4 to 1/3 were exotics.
Of course many of our most aggressive plants are exotics. Looking through a book on weeds, I discovered that 80 – 90% were from foreign countries. Those that were native were often listed because they toxic, alternate hosts for crop diseases, or water plants that blocked irrigation ditches. But some were also aggressive (“Invasive” is reserved for aggressive exotic plants.). These are often annuals such as ragweed and fleabane, but also include perennials such as prairie plants or red cedar trees.
However, aggressive natives often serve very important ecological functions. They quickly populate disturbed areas and often alter the environment so that other, more substantial plants can become established. These plants are then referred to as pioneer plants. In addition, as they are usually annuals, they produce large quantities of seeds which are utilized by birds and small mammals. As native plants, they also provide food for the larvae of butterflies, act as the food chain producers by feeding other insects and provide pollen for bees and other pollinators. Finally, they provide quick ground cover that reduces erosion.
Two examples of pioneer plants which I originally planted in my prairie patch which have virtually died out there, but have spread to other areas are pigeon peas and annual sunflowers.
I was not surprised to see poison ivy when I visited Terpstra’s gardens at the September meeting. I was a little surprised to see it listed among the plants they had. Of course, it does supply nutritious seeds for birds, but most of us would not allow it to persist in our gardens.
According to one source, “ragweed fruits are important food for many animals. They are favorite foods of Goldfinches, Juncos, Redwing Blackbirds, Bobwhites, Redpolls, White-crowned and White-throated Sparrows, and also are often eaten by certain mammals, such as Thirteen-lined Ground Squirrels and Least Chipmunks”. Again, I am sure there is enough ragweed growing elsewhere that I am not including it in my garden.
We may not be able to define a weed, but we all know it when we see it – and then we will pull it out or cut it down.