A deciduous shrub of erect, thinnish habit, up to 6 or 8 ft high, the twigs slender and glabrous except for a few scales. Leaves lanceolate or inclined to oblanceolate, slenderly pointed, 11⁄4 to 4 in. long, 1⁄2 to 11⁄4 in. wide; of thin texture; stalk 1⁄8 to 1⁄4 in. long. Flowers produced singly from each of a cluster of buds at the end of the naked shoots, sometimes as many as six at the tip of one shoot, often opening successively; flower-stalk 1⁄4 in. long, hidden by the scales of the flower-bud. Calyx small, shallowly five-lobed. Corolla pale rose-purple, opening widely, 11⁄2 to 2 in. across, five-lobed, downy outside. Stamens ten, their stalks downy at the base; anthers dark purple. Ovary covered with close, minute scales; style glabrous. Bot. Mag., t. 8304. (s. Dauricum)
Native of N. China, the Ussuri region of Russia, Korea, and Japan (where it is found only in the parts nearest to Korea – N. Kyushu and the Chugoku district of the main island). According to Wilson, it is abundant in Korea in thin woods and open country, and especially so in the north, where it forms the undergrowth of larch forest on volcanic soils. It was described in 1837 from specimens collected on the Pohuashan near Peking, and introduced from there to the Arnold Arboretum, USA, in 1882 by Dr Bretschneider. The first recorded introduction to Kew was in 1907, when plants were received from a Yokohama nursery, but Edinburgh had it nine years earlier from an unknown source.
Under cultivation the flowering season of this species varies according to the weather. At Kew, as a rule, it is at its best from Christmas to the beginning of February. I have seen it in splendid bloom on Christmas Day. The flowers are destroyed by about five degrees of frost, but are often succeeded by a fresh crop. After a hard winter and spring, flowers will open as late as April. This shrub must be included amongst the very best of winter flowerers, for few give so beautiful a display so early in the year. In botanical detail it scarcely differs from R. dauricum, but in its greater size and vigour, its larger more pointed leaves, and its larger flowers it is very different. It is also superior as a garden shrub.
R. mucronulatum has twice received an Award of Merit when shown from Kew: on February 12, 1924 (flowers purplish rose) and on January 8, 1935 (flowers light rose). It was given a First Class Certificate on January 22, 1957, when shown by the Crown Estate Commissioners, Windsor Great Park (clone later named 'Winter Sunset', flowers rich purplish rose).
cv. 'Cornell Pink'. – Flowers Phlox Pink (a pure medium pink with no hint of purple). It is a selection from over one thousand plants, raised by Henry T. Skinner at Cornell University, USA, from seeds of R. mucronulatum bought from the Yokohama Nursery Company in 1931. It was named and put into commerce in 1952 (R.C.Y.B. 1967, p. 132). Award of Merit when shown from Kew, March 30, 1965.