Plants have evolved elaborate mechanisms for detecting neighboring plants, which typically involve the perception of "cues'" inadvertently produced by their neighbors. Strigolactones are hormonal signaling molecules that are also exuded into the rhizosphere by most flowering plant species to promote arbuscular mycorrhizal symbioses. Since flowering plants have an endogenous perception system for strigolactones, strigolactones are obvious candidates to act as a cue for a neighbor's presence, but have not yet been shown to act as such.