Here's a bit of Red Clover, Trifolium pratense.
From Forage Plants and Their Culture:
"Red clover was not known as a crop by the ancient Greeks and Romans. It was apparently first cultivated in Media and south of the Caspian Sea, in the same general region where alfalfa was first domesticated. In Europe its use as an agricultural plant is comparatively modern, the first mention of its use as feed for cows being by Albertus Magnus in the thirteenth century. There are definite. records of its cultivation in Italy in 1550, in Flanders in 1566, in France in 1583. From Flanders it was introduced into England in 1645, and shortly afterwards its culture was described in several books. Its use in Europe became extensive about the end of the eighteenth century.
It was probably introduced into the United States by the early English colonists, but the first published mention of its culture was by Jared Eliot, who wrote of its being grown in Massachusetts in 1747."
From The Farmer's Manual:
"Some farmers complain that red clover, when sown for mowing upon their orchard grounds, causes the trees to wither and decay. This may be remedied by sowing plaster of Paris upon your clover; your orchards will flourish as well as upon English mowing; one bushel to the acre in the spring, or fall, annually, will answer. It is of no consequence to inquire, why a crop so fertilizing as clover, should injure the orchard, nor why the plaster should prevent it; facts are stubborn things, and are generally, all that are of importance in good farming."
Piper, Charles Vancouver. Forage Plants and Their Culture. New York, 1916. 361-2. Web. Google Book Search. 18 Jul 2009.
Butler, Frederick. The Farmer's Manual. Hartfort, CN, 1819. 7. Web. Google Book Search. 18 Jul 2009.