Invasive Species in an Urban Flora: History and Current Status in Indianapolis, Indiana

Abstract

Invasive plant species are widely appreciated to cause significant ecologic and economic damage in agricultural fields and in natural areas. The presence and impact of invasives in cities is less well documented. This paper characterizes invasive plants in Indianapolis, Indiana. Based on historical records and contemporary accounts, 69 of the 120 species on the official Indiana state list are reported for the city. Most of these plants are native to Asia or Eurasia, with escape from cultivation as the most common mode of introduction. Most have been in the flora of Indianapolis for some time. Eighty percent of Indianapolis’ invasive herbaceous plants were present before 1940, but only 14% of woody invasive plants were known to be present in the city at that time. The largest group of woody invasives is shrubs. Newly present invasive plants continue to be reported for Indianapolis. Expert opinion rates Callery Pear, Japanese knotweed, and Japanese stiltgrass as the greatest emerging threats.