Published online by Cambridge University Press: 12 June 2017
2-chloro-4,6-bis(ethylamino)-s-triazine (simazine), ethyl N,N-di-n-propylthiolcarbamate (EPTC), and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) were shown to aid in the establishment of rose clover (Trifolium hirtum All.) and harding-grass (Phalaris tuberosa L. var. stenoptera (Hack.) Hitch.) by reducing competition from resident annual plants, primarily medusahead (Elymus caput-medusae L.). The success of preemergence herbicides was shown to depend on fall precipitation in amounts great enough to permit seed germination and plant growth before winter temperatures become limiting. The degree of weed control necessary to aid in seedling establishment was low, sometimes lower than could be measured by estimates of ground cover.