Thousands of non-native plant species have been introduced and naturalized outside of their native ranges. A small portion of these naturalized species go on to become invasive, spreading away from sites where they initially naturalized and causing negative ecological impacts. In some cases, abiotic limitations, such as cold temperatures, prevent naturalized species from becoming invasive within all or a portion of their non-native range. However, rising temperatures due to climate change could lead to rapid population growth of some naturalized populations, triggering new invasions of these ‘sleeper populations’. Here, we present a database of impact assessments for 179 species naturalized in one or more northeastern state (CT, MA, ME, NH, NY, RI, VT). This database can be used to prioritize invasive species management to prevent the awakening of high-impact sleeper populations.