This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
A perennial glabrous marsh herb, with creeping rootstocks, alternate long-petioled 3-foliolate basal leaves, and white or purplish flowers, racemose or panicled on long lateral scapes or peduncles. Calyx 5-parted, the segments oblong or lanceolate. Corolla short-funnelform, 5-cleft, its lobes induplicate-valvate, fimbriate or bearded within, spreading. Stamens 5, inserted on the tube of the corolla; filaments filiform; anthers sagittate. Disk of 5 hypogynous glands. Ovary 1-celled; style subulate, persistent; stigma 2-lamellate. Capsule oval, indehiscent or finally rupturing. Seeds compressed-globose, shining. [Greek, perhaps month-flower, name used by Theophrastus.]
A monotypic genus of the cooler parts of the northern hemisphere.
Menyanthes trifoliata L. Sp. Pl. 145. 1753.
Rootstock thick, scaly, sometimes 1° long, marked by the scars of bases of former petioles. Leaves 3-foliolate; petioles sheathing at the base, 2-10' long; leaflets oblong or obovate, entire, obtuse at the apex, narrowed to the sessile base, pinnately veined, 1 1/2 - 3' long; raceme borne on a long scape-like naked peduncle, arising from the root-stock, 10-20-flowered; pedicels stout, 3"-l2" long, bracteolate at the base; flowers 5"-6" long; calyx shorter than the white or purplish corolla, which is bearded with white hairs within; stamens shorter than the corolla and style exserted, or longer and style nearly included; capsule ovoid, obtuse, about 4" long.
In bogs, Greenland to Alaska, south to Long Island, Pennsylvania, Minnesota, Nebraska and California. Also in Europe and Asia. Water- or bitter trefoil. Water-shamrock. Moon-flower. Marsh-clover. Bitter worm. Bog-nut. Brook-bean. May-July.