A number of species of sweet clover are found throughout the world, and
most of them are native to temperate Europe and Asia as far east as
Tibet.
White sweet clover,[1] yellow biennial sweet clover,[2] and yellow
annual sweet clover[3] are the only species which have given sufficient
promise as forage and green-manure crops in this country to warrant
growing them under cultivation.
[1] _Melilotus alba_ Dear.
[2] _Melilotus officinalis_ (L.) Lam.
[3] _Melilotus indica_ (L.) All.
It is difficult for the average person to distinguish between the
different species of sweet clover from an examination of the seeds
or seed pods only. The differences are indicated in figure 1. Where
there is a question as to the identity of a sample of seed it should
be sent to a State agricultural experiment station or to one of the
seed laboratories of the United States Department of Agriculture for
identification.