Growing form
Annual/biennial herb.
Height
40–150 cm (16–60 in.). Stem ascending–erect, almost glabrous.
Flower
Corolla zygomorphic, yellow, 4–7 mm (0.16–0.28 in.) long, fused at base. Petals 5; the upstanding the ‘standard’, the lateral two the ‘wings’, the lower two united to form the ‘keel’, overall shape of corolla being butterfly-like, keel shorter than other petals. Calyx 5-lobed. Stamens 10. A single carpel. Inflorescence an axillary, long raceme; flowers nodding.
Leaves
Alternate, stalked, stipulate. Blade with 3 leaflets, terminal leaflet stalked. Leaflets elliptic–lanceolate, with toothed margins. Stipules entire.
Fruit
3–5 mm (0.12–0.2 in.) long, glabrous, with horizontal wrinkles, when ripe yellowish brown, usually 1-seeded, indehiscent pod (legume).
Habitat
Roadsides, railways, harbours, rubbish tips, waste ground, yards.
Flowering time
July–September.

Ribbed melilot was mentioned in an ancient medicinal book, but in the Middle Ages the plant was completely forgotten about, and when it started to be used again there were differences of opinion about its effects: some regarded it as poisonous while others thought it a good medicinal plant. As is the case for all medicinal plants, the correct dosage and process is important for ribbed melilot too. The plant’s active ingredient is cumarin, which smells pleasantly sweet. Its aroma has led it to be used in tobacco mixes and in special cheeses, and to cover up the bad taste of other medicines. It is antiseptic and has been used t treat infections and wounds. Cumarin is toxic in large doses – it is used as an insect poison – so it is good to be careful to avoid an overdose.

Ribbed melilot looks like white melilot (M. alba), and the species often grow close to each other. It is clearly the rarer of the two in Finland and grows quite sparsely in some areas. It seems to thrive better inland to some extent than it does at the beach, where white melilot is rife. It is not really possible to rely on the flowerless stems to differentiate the species, but it is much easier when they are in bloom because ribbed melilot’s are yellow and white melilot’s are white. In the seed stage ribbed melilot’s pod is clearly stalked while white melilot’s on the other hand is basically stalkless. Flowering ribbed melilot can be confused with tall melilot (M. altissimus), which is yellow-flowered and very rare. Telling the species apart demands a close inspection of the corolla: tall melilot’s petals are on average the same length, but ribbed melilot’s keel is shorter than the wings and standard. Tall melilot is clearly more sensitive to the cold than its relatives and in practice it only grows in Finland in places where it originally landed in sailing boats’ ballast soil: on waste ground in harbours squeezed between asphalt areas and terminals.

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