I review the role of bees in the pollination of invasive plants. I then explore how invasive plant-bee interactions could affect bee communities. I present results from an investigation of purple loosestrife (Lythrum salicaria L) effects on the density and composition of bee communities in New Jersey, USA. Comparisons of six invaded and seven uninvaded sites showed that bee densities were higher in invaded sites, but only significantly in one of four sample periods. Purple loosestrife attracted visitors from >12 bee genera. Native Bombus spp. comprised 54%, introduced Apis mellifera 29%, and other native bees combined 13% of all visitors to purple loosestrife. I categorized bees into two functional groups based on body size. Bee communities in invaded sites differed from those in univaded sites. Invaded sites were dominated by large bees (mainly Bombus), whereas uninvaded sites were dominated by small bees (Halictus, Lasioglossum, Ceratina, and others). Purple loosestrife appears to favor large bees over small bees. The longer foraging distances of large bees may allow them to fly in from surrounding habitats to exploit the purple loosestrife bloom. Small bees may suffer from reduced densities of native flowers in invaded sites.