A seed field of bolting onions is extremely difficult, if not impossible, to weed satisfactorily by hoeing or any mechanical means without serious reduction in seed yield, because of the ease with which seed stalks are broken. Injury to seed stalks results in lower seed yields, but if the weeds are allowed to grow they also reduce seed yields. The presence of weed seeds makes cleaning more difficult and may reduce yields further, because foreign material and weed seeds can rarely, if ever, be separated satisfactorily without the removal of some crop seed. Actually few, if any, commercial growers practice either cultivation or handweeding after the onion crop has begun to go to seed. Consequently, exceptionally weedy fields are common in onion-seed-growing sections. The use of herbicides as a possible solution to this difficult problem has been studied in Utah since 1949, with some promising results.