Landscaped parks Central Park thumb|right|American elm trees along the Mall and Literary Walk in New York City's Central Park (2013) The oldest American elm trees in New York City's Central Park were planted in the 1860s by Frederick Law Olmsted, making them among the oldest stands of American elms in the world. Along the Mall and Literary Walk four lines of American elms stretch over the walkway forming a cathedral-like covering. A part of New York City's urban ecology, the elms improve air and water quality, reduce erosion and flooding, and decrease air temperatures during warm days.Central Park Conservancy. The Mall and Literary Walk .
Landscaped parks Central Park thumb|right|American elm trees along the Mall and Literary Walk in New York City's Central Park (2013) The oldest American elm trees in New York City's Central Park were planted in the 1860s by Frederick Law Olmsted, making, them among the oldest stands of American elms in the world Along the Mall and Literary Walk four lines of American elms stretch over the walkway forming a cathedral-like covering. A part of New York City's urban ecology, the elms improve air and water quality reduce erosion and flooding, and decrease air temperatures during warm days.Central Park Conservancy. The Mall a.nd Literary Walk .