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.
Fig. 2.—A branch of white sweet clover, showing the long, loose racemes which bear white flowers.
White sweet clover ([fig. 2]) is ordinarily referred to as melilotus or meliot in the South and merely as sweet clover in other portions of the country. When soil conditions are favorable for germination, sweet-clover seedlings will appear from one to two weeks after seeding. On account of the biennial nature of the plants, they do not seem to make much growth above ground the first month or six weeks after germination, but during this time they are developing root systems rapidly and thus becoming established, so to be able to withstand adverse conditions. Plants which have made no more than 2 inches of top growth very often have produced roots 6 inches or more in length ([fig. 3]). The tap-root continues to develop rapidly throughout the growing season the first year, and by autumn often reaches a length of 24 to 36 inches and a diameter of three-fourths to 1 inch at the crown.