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A dwarf, much-branched evergreen shrub about 6 in. to 9 in. high, of tufted habit. Leaves linear, blunt, much crowded, 1⁄4 to 1⁄2 in. long, 1⁄16 in. or less wide, minutely toothed, dark glossy green. Flowers produced in June and July singly on a slender, glandular stalk up to 11⁄2 in. long, or in an umbel of three or four flowers. Corolla bluish purple, pitcher-shaped, nodding, five-toothed, 1⁄3 in. long. Calyx with five lance-shaped, downy lobes; stamens ten, and, like the style, included within the corolla.
Native of high alpine summits and high latitudes in Europe, Asia, and N. America. It is found in Scotland in a few localities on the border between Perthshire and Inverness-shire (Forest of Atholl and Badenoch), but had, and may still have, a wider distribution. There are old specimens at Kew from near Aviemore and the Isles of Shiant. Under cultivation it succeeds better in the north of England and in Scotland than in the south, where the summers are too dry and hot for it, and cause its foliage to drop prematurely. It is, consequently, uncommon. In the Botanic Garden of Edinburgh it thrives very well. It should be planted in peat and sphagnum moss mixed, and have a surfacing of the latter also. One of the most interesting of British plants, and distinct in this genus because of its colour. It is figured in: Ross-Craig, Draw. Brit. Pl., Pt. XIX, t. 29.
Two forms of P. caerulea were exhibited by R. B. Cooke in 1938, one from Japan with red-purple flowers, the other, with paler flowers, from Norway. Both received an Award of Merit.