The clover growing area of the United States embraces the states of California and Tennessee and all the region lying north of the parallel of 36° north latitude, between the Rocky Mountains on the west and the Atlantic Ocean on the east. In this part of the United States Red Clover has become an important agricultural plant. Clover seed is shipped by the carload from place to place and even across the water.
It is a well known fact that clover seed is one of the most impure seeds on the market. The majority of our troublesome weeds are naturalized species, and not a few of them have come to us in impure clover seed. Constantly, farmers are complaining that the seeds of bad weeds have been sold to them in clover seed, and it is true that our seedsmen are largely responsible for the dissemination of Ox-eye Daisy, Plantain, Sorrel, Fox-tail, etc. So frequently has the attention of Experiment Station workers been called to the question of impure clover seed that some of the stations have made investigations and published the results in their bulletins. Work of this kind has been done at the North Carolina and Michigan stations. Their reports show that the subject is really one of great importance. Prof. McCarthy says,1 “Every bushel of uncleaned clover seed contains from three to five pounds of weed seeds.” Again he says,2 “Uncleaned Red Clover seed is probably the foulest seed on the market."
Stewart, F. C.
"The impurities of clover seed,"
Bulletin: Vol. 2
, Article 9.
Available at: https://lib.dr.iastate.edu/bulletin/vol2/iss21/9