A tiny evergreen shrub 3 to 5 in. high, forming a low tuft of gnarled twigs. Leaves crowded, hard and leathery, narrowly obovate or oblong, tapered towards the base, obtusely pointed or rounded at the tip, thickened at the margins, and triangular in section, 1⁄4 to 1⁄2 in. long, 1⁄16 to 1⁄12 in. wide, not stalked, dark green. Flowers rich glowing pink, fragrant, produced in June in terminal clusters of about four blossoms; the tube of the flower is slenderly cylindrical and covered with fine down; across the spreading oval lobes the flower is 1⁄4 to 1⁄3 in. in diameter.
Native of the mountains west of the northern end of Lake Garda, where it now inhabits inaccessible cliffs of dolomitic rock, safe from the depredations of greedy collectors, who have exterminated it in its more easily reached stations. When the first edition of this work was published the most successful cultivator of this lovely alpine shrub was Reginald Farrer, who used to show little bushes grown in pots at the Temple Show in London, almost covered with blossom. In recent years specimens equally fine have been exhibited at the R.H.S. Hall.
It was in the year that this work was first published, in 1914, that Dr Jenkin and Robert Tucker collected the parent of the clone ‘Grandiflora’, which has larger flowers than the forms previously cultivated and has now almost displaced them in cultivation. (For a coloured illustration see Journ. R.H.S., Vol. 91, fig. 117 – of a fine potted specimen grown by Mrs Greenfield of Epsom.)
Propagation is usually achieved by grafting on to seedling stocks of D. mezereum, but evergreen species are also used as the stock and are perhaps preferable. Cuttings, though they strike readily enough, do not grow or flower so well as grafted plants. D. petraea is perfectly hardy and will grow well in the open ground if given a place in full sun with a deep and moist root-run in gritty soil with lime added. Its full beauty and delicious scent is, however, best enjoyed when it is grown as a pot-plant. For its cultivation the reader will find detailed guidance in an article by Will Ingwersen in Bull.A.G.S., Vol. 20, pp. 71-73, and in Frank Barker, The Cream of Alpines.
D. × thauma Farrer – A hybrid, probably between D. petraea and D. striata, found by Farrer on the Cima Tombea. It is of little garden value, being reluctant to flower, and like the second parent, difficult to keep happy in cultivation. A similar plant, perhaps of the same parentage, was cultivated at Kew but proved impossible to propagate and has died.
D. arbuscula Čelakovsky – A dense, evergreen bushlet usually not exceeding 8 in. in height; branchlets stout, slightly downy or glabrous, reddish when young. Leaves oblong, 2⁄5 to 1 in. long, blunt at the apex, furrowed along the midrib, margins revolute; dark green and glabrous above, downy beneath when young, later more or less glabrous. Flowers pink, borne in terminal clusters of three to eight; tube about 5⁄8 in. long.
A rare native of the Carpathians of E. Czechoslovakia, discovered by A. Richter in 1855, at which time its habitat lay in Hungarian territory. It is closely related to D. petraea, but differs in its foliage characters and reddish young stems, and prefers a lime-free soil. It is also easier to cultivate. See further in Bull. A.G.S., Vol. 39, pp. 129-134.