For a field guide to invasive species in Concord, see: http://www.concordma.gov/Pages/ConcordMA_Bylaws/invasives For a town GIS map of invasive species, see: http://www.mapsonline.net/concordma/index_plants.phtml Problem Trees: Black Locust, Norway Maple, Tree-of-Heaven, Autumn-olive Problem Small Trees and Shrubs: Common Buckthorn, Glossy Buckthorn, European Hedge-Privet, Japanese Knotweed