Most turfgrasses are not native to the U.S. but have naturalized in some locales during the past 200-plus years. Identification of turfgrasses as invasive species is problematic because human activity has disrupted natural environments and the extent of environmental harm caused by naturalization of turfgrasses is unknown. The ability of turfgrasses to outcompete native species is undocumented partly because the time frame for plant succession can be long-term and capable of being altered by human activity and natural events such as fire and herbivory. A number of invasive plant characteristics have been identified but not all invasive plants possess those characteristics therefore valid predictive models do not exist. Data on invasiveness of turfgrasses in natural environments are rare. A southern California study showed increased biodiversity enhanced establishment of Agrostis stolonifera when seed was planted in sedge tussocks, refuting the idea biodiversity is important for preventing non-native species establishment. Between 1965 and 1981, the presence of A. stolonifera increased in shaded, wind-protected sites on the sub-Antarctic Marion Island while the indigenous A. magellanica persisted in exposed sites: A. stolonifera had better photosynthetic efficiency while A. magellanica had stronger shoots. When Poa pratensis and native prairie plants were seeded in bare soil in Minnesota, P. pratensis thrived when irrigation and fertilizer were applied. Native vegetation dominated in the absence of irrigation and fertilization. Studies indicate tremendous variation in spreading potential exists among varieties of turf species. Data are needed to determine the requirements for, and likelihood of, successful colonization of turfgrasses in natural ecosystems. Variables include ecosystem type (e.g., riparian or dry upland), existing vegetation type and density, climate, and genotypic variation within turf species. A national survey map of turfgrass communities and site history would be helpful in determining the invasive potential of turfgrasses.