This section is from the book "British Wild Flowers - In Their Natural Haunts Vol2-4", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
In spite of its numerous pods this plant is not found in any ancient deposits. The North Temperate Zone is its principal region, the plant being found in Europe, East and Western Asia, Thibet, and it has been introduced into North America. In Great Britain it is not known in Brecon, Radnor, Carmarthen; in N. Wales only in Carnarvon, Flint, and Anglesea; in the Trent province generally; not in the Isle of Man, Dumfries, Kirkcudbright, Ayr, but in Berwick and Haddington, Edinburgh, Fife, W. and N. Perth, from which county it is generally distributed southward. In Ireland it is very rare.
Watson regarded the sweet-scented Melilot only as a denizen, in which case we could not expect to find it in British Glacial or Preglacial beds. It grows in waste places, reaching a great height, growing generally in profusion, and once established it continues in the same locality for a long period. With it are associated Worm-seed, Lepidium Draba, and other weeds of cultivation.
The plant is of erect habit. The stem is much branched. The leaves are trifoliate. The leaflets are blunt, coarsely toothed, egg-shaped or inversely egg-shaped, linear to oblong. The stipules are awl-like, very slender, entire. The leaves go to sleep at night, and the leaflets assume a vertical position, facing north, and facing the terminal leaflet, so that the upper surfaces face N.N.W. and N.N.E. The terminal leaflet twists west or east, usually west.
Darwin also found that if horizontal the leaves suffered from frost. He says the terminal leaflet moves in another and more remarkable manner, for whilst its blade is twisting and becoming vertical, the whole leaflet bends to one side, and invariably to the side towards which the upper surface is directed, so that if this surface faces the west the whole leaflet bends to the west, until it comes into contact with the upper and vertical surface of the western lateral leaflet. Thus the upper surface of the terminal and of one of the two lateral leaflets is well protected.
The flowers are yellow, in racemes, all turned one way. The petals are nearly equal. The wings are keeled. The corolla is more than twice as long as the calyx. The ultimate flower-stalks are short. The pod is egg-shaped, flattened, acute, long-pointed, netted, hairy, black when ripe, 1-2 seeded.
Melilot grows often 4-5 ft. high, but usually 2 ft. The flowers are in bloom from June to August. The plant is an annual reproducing by seed.
In most respects the floral structure of Melilot is like that of Dutch Clover or Medicago. But the calyx is not so long as in the former. It is also more expanded, so that the petals, which are longer, have much greater freedom of movement. The cells of the alae or wings are at one point interwoven with those of the keel as if grown together, and when one is moved the other of necessity must also move, whilst at the same time both return together to their former position when pressure is removed. The wings and keel are able to rotate further downwards, the claws not being adherent as in Dutch Clover; and by aid of the finger-like processes, which here replace the pouches of the latter at the superior basal angle of the wings, they return to position. These processes clasp the central staminal column above, about a quarter of the way from the base. They separate when the carinae are drawn down, springing back and clasping it as before. The stigma projects beyond the anthers. Cross-pollination is therefore the rule. Melilot is visited by Hymenoptera, Apidae, Sphegidae, Tenthre-dinidae.
Photo. Flatters & Garnett - Melilot (Melilotus Officinalis, Lam.)
The seeds are dispersed by the plant's own action. The pod is short and straight, with few (1-2) seeds, which are scattered when the pod falls owing to the pedicel rotting away, or by the opening of the pod.
Melilot is one of the sand-loving plants which subsist best on a sand soil. It is common on Keuper Marl or the sands of the Boulder Clay.
A fungus, Peronospora viciae, grows upon it. The beetles Meligethes flavipes, Apion tenue, A. meliloti, Sitones meliloti; and the Lepidoptera, Mazarine Blue (Nomiades (Lycaena) semiargus), Small Angle Shades (Euplexia Lucipara), Latticed Heath (Strenia Clathrata), Grass Eggar (Lasiocampa Trifolii) Feed On It.
Melilotus, Pliny, is from mel, honey, lotus, Theophrastus; and the second name refers to its use in medicine. It is called Hart's, King's, or Plaister Clover, Whuttle Grass, Heartwort, King's Crown, Wild Laburnum, the last in allusion to the resemblance between the flowers and Laburnum.
In ancient Greece Melilot was worn in garlands and chaplets. It was said to have sprung from the blood of a lion slain by the Emperor Hadrian. Melilot smells like new-mown hay. It used to be much cultivated, but is now replaced by Lucerne, Clover, and Sainfoin. In Switzerland they use it to flavour Gruyere cheese, the flowers and seeds being bruised and mixed with the curd before being pressed. Doubtless the luxuriance of the meadows generally has much to do with its richness.
Essential Specific Characters:77. Melilotus officinalis, Lam.- Stem tall, erect, leaflets narrow, ovate, serrate, flowers in racemes, yellow, lateral, petals equal, legumes hairy, wrinkled, acute, wings keeled.