On 16th Street in Washington, D.C., the answer is a city remembering the people it lost in World War I. The Association of the Oldest Inhabitants of the District of Columbia notes the city planted the first of 507 Norway maples there on May 30, 1920, as a memorial to its war dead. You have probably walked down a leafy street without giving a second thought to who planted the trees. Each tree was dedicated to a local war casualty. The idea was simple and kind. But a century later, those trees have moved on to a surprising second act.
Norway maple is a non-native tree, and it now also grows in nearby Rock Creek Park. The National Park Service explains in its guide to the park’s forests that one community there, called the Basic Mesic Hardwood Forest, sometimes includes Norway maple. The agency describes the species as an aggressive invader and lists the tree among the invasive plants that threaten that forest. Plants on the list also include English ivy and garlic mustard. Invasive plants can degrade animal habitat and compete with native plants for soil nutrients, sunlight, and pollinators. It just means that the same attributes that make a forest lush can also make it a target.
The fertile soils that allow native plants to flourish also attract invaders, according to the guide.
