An important route of introduction of some nonnative species that subsequently become invasive in the United States is through horticulture. One such plant is Euonymus fortunei (Turcz.) Hand.-Maz., commonly known as wintercreeper, an evergreen groundcover with more than 52 different horticultural varieties, which is still sold at many plant nurseries and garden centers in the midwestern United States. Although several states have recognized E. fortunei as an invasive species, it is unknown how its escape from cultivation has occurred and even the identity of spreading populations, including whether hybrids or cultivars are involved. Using codominant microsatellite markers, we sampled multiple invasive populations in Ohio, Kentucky, Kansas, and Minnesota and compared their genotypes with commercially available cultivars to determine how spread has occurred. All samples collected from invasive populations were genetically identical to one another and matched perfectly with the 'Coloratus' cultivar, the only cultivar to exhibit polyploidy. The data also suggest that E. fortunei may potentially reproduce via apomixis and/or clonally through propagule fragments, which can quickly fix favorable genotypes within a population. To curb continued invasive spread, we suggest that Coloratus be removed from commercial sale and distribution. We also propose that land managers, horticultural and landscaping businesses, and governmental agencies carefully monitor other Euonymus cultivars for invasive potential and spread.