This section is from the book "A Manual Of Weeds", by Ada E. Georgia. Also available from Amazon: A Manual Of Weeds.
Introduced. Biennial. Propagates by seeds. Time of bloom: June to October. Seed-time: August to November.
Range: Throughout North America except the far North. Habitat: Roadsides and waste places; common about towns.
The Sweet-clovers are natives of Central Asia but came to us from Mediterranean Europe, where for centuries they have been grown for forage and as honey plants. Weeds only when they are permitted to make highways and by-places unsightly with thickets of dying stalks. Their good qualities are many. First, they are
"soil renovators," partly by reason of their large and deeply penetrating roots, which break up the soil, mellow, aerate, and drain it, and then, by their death and rapid decay, furnish it with humus; also they bear on their roots many tubercles in which live those beneficent, nitrogen-gathering bacteria that make the earth better for their having lived in it. For this reason, Sweet-clover is often used to prepare the ground for the growing of Alfalfa. The hay is nutritious, but cattle do not like its strong odor and will not eat it until they have been "educated to the taste," which is usually done by turning them into the Sweet-clover field early in spring, when no other green forage is available. (Fig. 165.)
Stems three to ten feet tall, round, slender, somewhat woody, many-branched, smooth except the young growing twigs, which are finely hairy. Leaves pinnately three-foliolate, the leaflets oblong to elliptic, obtuse or sometimes even notched at the tip, very finely toothed, the foot-stalk of the middle one bent slightly upward; petioles usually shorter than the blades. Flowers in long, slender, one-sided, axillary racemes, white and very fragrant; corolla about a quarter-inch long, with narrow petals, the standard longer than the wings or the keel. Pods ovoid, wrinkled, net-veined, one- or two-seeded. When in the soil the seeds are said to retain their vitality for fifty years or more; they are sometimes used by unscrupulous dealers for the adulteration of Alfalfa seed, which is somewhat similar in appearance but much more expensive.
Close cutting as soon as the first flowers open; the plants will immediately sprout thick stools of flowering stalks, requiring a second and perhaps a third cutting, but if no seed is allowed to mature and drop into the soil there will be no further trouble, for when it has flowered the plant dies. Small areas may be more quickly hand-pulled.
Fig. 165.- White Sweet-clover (Melilo-tus alba). X 1/3.