Some plants use allelopathy to compete against neighbouring plants, and the ability to induce allelopathic compound production in response to competition is hypothesized to be adaptive, as plants can save costs of metabolite production in the absence of competitors. However, whether plants induce allelopathy has rarely been explored so far. We studied the inducibility of polyacetylenes—putative allelopathic compounds in Solidago altissima—in response to competition. Polyacetylenes were found in natural soil surrounding S. altissima patches within...