This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Seeds and other parts of this plant are known from Neolithic deposits in Renfrewshire. Hence it is a fairly ancient species. It is found in Arctic Europe, N. and W. Asia, and N.W. America. In Great Britain it is absent from N. Wilts, N. Essex, Bucks, Suffolk. W. Norfolk, Cambridge, Mid Lancs, Main Argyle, northward to the Shetland Islands, but is general elsewhere. It ascends to an altitude of 4000 feet. It is native in Ireland.
Whortleberry is a typical heath plant, growing as a rule at a considerable altitude, but always under ericetal conditions. Hill-sides, woods, and copses are similar stations for this plant, which loves a subsoil or soil rich in humus, like that of a wood or heath. Whole botanical districts are made up of this species, so that it gives its name to a certain type of association.
This is a short, shrubby plant, with the stem at first prostrate, then ascending and branched. The stem is smooth, angular, green, rigid. The leaves are egg-shaped, coarsely toothed, falling in autumn, the nerves net-veined. The stems as well as the leaves are capable of assimilation.
The leafless flower-stalks are 1-flowered, the flowers solitary, and pinkish, waxy, greenish, nodding or drooping. The corolla is swollen below, narrow above, with a narrow entrance. The anthers have two bristles or horns on the back. The fruit is a berry, nearly black or dark-blue, with a greyish bloom, or bluish-green. The calyx-tube is conical.
The height of the plant is at most 18 in. It is flowering in April, May, and June. The plant is a shrub increased by layers, and worth cultivating.
It is slightly proterandrous, the anthers ripening first. The pollen is dry and dust-like. Honey is secreted by an annular ridge resting on the ovary which surrounds the style, which is never moist, and not so smooth as most honey-glands. Honey drops are found on the outside of the base of each stamen, passing between the anther-stalks and the wall of the corolla. The honey is secreted in abundance in the globular corolla by the epigynous disk. The aperture is so small that only long-lipped insects are able to reach it, such as hive-bees and humble-bees. The flowers resemble those of the Heath; but the anther-cells are close to the style, resting against the openings, and so retained until the insect visitors disturb it, when pollen falls on the back. The stigma is slightly projecting, and each visitor touches the stigma before it receives the pollen with which the anthers cover it. It is visited by the honey-bee, Bombus agrorum, B. lapidarius, B. terrestris, B. scrimshiranus, and Andrena.