Butterflyweed is appropriately named because it is a good plant to attract butterflies to a garden. It is a member of the milkweed family and will grow in poorer soils.
Crown vetch, a plant found in our area, was created by researchers at Penn State University to help stabilize road sides - that it does. It also has a habit of spreading to areas where is was never planted and can take over areas while outcompeting native plants.