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.
This little woodland flower is local but widespread, and known throughout the Northern Temperate Zone in Europe, but not in Prussia, Greece, and Turkey. No early records are extant. The Wood Loosestrife grows in every part of Great Britain except Hunts, S. Lincs, and the Shetlands. In the Highlands it ascends to 2500 ft.
Watson regards it as a frequent but not quite common plant, and possibly occurring everywhere except in Huntingdon, being local in Bedford and Cambridge. Thus it is not common in the more low-lying damp districts of the central plain. Generally it occurs in woods, loving a shady habitat, and under hedges in wooded districts.
The stems of the Wood Loosestrife are usually lying on the ground, numerous, furrowed each side, reddish, rooting at intervals. The leaves are opposite, stalked, egg-shaped, acute, glossy, yellowish-green, with marked veins. The flowers are yellow, small, on flower-stalks in the axils, longer than the leaves, 1-flowered and slender. The calyx is deeply divided into 5 or 6 segments, which are narrow and awl-like, sub-triangular, and do not fall. The corolla, which is wheel-shaped, has no limb, and is divided into 5 or 6 egg-shaped segments, with small yellow glands in the mouth, between the anther-stalks, which are distinct, not united, and smooth. The capsule is 5-valved, globular, and contains numerous round, flat seeds.
The plant is rarely more than 3 in. in height. The flowers are in bloom from May till July. Wood Loosestrife is a perennial, which can be propagated by division, and is worth cultivating.
In this the stamens and style are included, as in Yellow Loosestrife. The yellow monopetalous or tubular corolla has no limb, but glands between the anther-stalks at the base, where it is brighter yellow. The stamens are erect and thicker in the middle, the anthers are oblong and rather prostrate, rising up at the end, the whole flower is less campanulate or bell-shaped, and more like that of a pimpernel. The style is club-shaped and threadlike, and the stigmas simple. Growing in woods it is little visited by insects, as there is no honey, and if so it is easily accessible, while self-pollination can readily occur without insects.
Photo. J. H. Crabtree - Wood Loosestrife (lysimachia Nemorum, L.)
The capsule splits open by 5 valves, and the seeds are numerous, and dispersed by the shaking of the capsule by the wind.
This is a clay-loving plant, and addicted to a clayey soil, but it also requires some amount of humus.
The first botanical name is the Greek for loosestrife, and the second Latin name refers to its habitat in groves or woods.
The only English name is Yellow Pimpernel.
Essential Specific Characters: 203. Lysimachia nemorum, L. - Stem prostrate, spreading, leaves ovate-acute, opposite, flowers yellow, small, axillary, on 1-flowered peduncles, filaments free, glabrous.