The rapid spread of invasive species threatens the structure and functioning of native communities. Japanese knotweed (Fallopia japonica) forms monotypic stands in North American and European riparian zones, and is particularly common in disturbed urban settings. Here, we contrast the leaf-processing rates and macroinvertebrate community composition of Japanese knotweed and a common species, Acer saccharum (sugar maple). We monitored 4g leaf packs in Kayaderosseras Creek, a semi-urban stream in upstate New York, from Oct 11 – Nov 28, 2006. Processing rates were slower for Japanese knotweed than sugar maple (k = 0.031 and 0.039, respectively). Both processing rates are unusually quick, a pattern that may be typical of urban streams. Sugar maple included more arthropods per unit leaf mass than did knotweed, and community composition varied among the two leaf types on three of the four collection dates. Our study is the first to demonstrate that leaf processing rates and community development differ between the invasive knotweed and a common native species.