The problem of tree species choice for city ornamentation purposes in Moscow is acute due to increasing anthropogenic environmental stress. Most of native and alien tree species appear to be highly susceptible to harsh city environments. The North American box elder is an invasive alien species no longer controlled by humans. The aim of our research was to develop a scientifically based approach to the use of this species in ornamentation of ecologically problematic areas of Moscow. High seed yield and germination success lead to formation of box elder stands comprised by bent and crooked trees without any control by man. However, growing box elder plants under controlled conditions (keeping up the rules of planting and growing ornamental trees) leads to formation of upright ornamental trees. High grow rate, lack of any serious diseases and pests, high ecological sustainability enable to grow trees suitable for ornamentation of streets with high traffic load fast and cheap. Light initialization of sleeping buds by means of cutting enables to improve crooked and bent trees. Thinning out existent box elder thickets by eliminating mostly female trees may improve the situation as well. The analysis of literature indicates that full elimination of this species from the city tree stands may make the city environmental situation worse. However, in areas where other tree species may grow, the box elder should be completely eliminated.