There is heightened interest in the effects that the provenance of plants in the landscape has on animals inhabiting them. This topic is of great interest for designers of urban ornamental landscapes, which tend to be mosaics of native and exotic plants. Although there is a substantial body of research on insect herbivores, less attention has been paid to arthropod natural enemies. Many commonly grown exotic woody plants were missing from eastern North America for millions of years prior to the arrival of Europeans. Due to the lack of a recent co-evolutionary history with these exotic plants, native natural enemies may be less well able to use the resources provided by them—architectural features and nutritional supplements—than they will those of native plants. Hence, natural enemies will be less numerous and diverse in landscapes dominated by exotic plants. To test this hypothesis, we designed a replicated experiment comprising 0.08-hectare plots planted to congeneric pairs of 16 genera of woody plants from either Eurasia or North America. Spiders attending egg masses of the brown marmorated stink bug, Halyomorpha halys, (Stål) (Hemiptera: Pentatomidae) emplaced on leaves of a subset of plant species known to be attacked by this pest, were statistically less abundant in the exotic plots, thus supporting the hypothesis.