P. japonica of horticulturists (not P. japonica of Thunberg).
Tree twenty to thirty feet in height, vigorous; trunk six to twelve inches in diameter, straight; bark thick, rough, numerous corky elevations especially on the branches, reddish or cinnamon-brown, peach-like; branches long, upright-spreading, much forked, brash and often splitting at the forks; branchlets thick, straight, glaucous and glabrous, at first light red, growing darker the second year; lenticels few or many, usually small but conspicuous, light in color.
Winter-buds small and obtuse, free or appressed; leaves borne abundantly, small or of but medium size, oblong-obovate, point acuminate or abrupt, prominent, base rounded, firm, thin, membranaceous, margins finely and closely serrated, sometimes in two series, teeth usually glandular; upper surface bright green, glabrous, lower surface dull, whitish, glabrous or slightly pubescent on the veins; veins pronounced; petioles one-half inch in length, stoutish, tinged with red; glands few or several, usually globose, greenish; stipules lanceolate, very narrow, one-half inch long, caducous.
Flowers expanding early, before, with or sometimes after the leaves, first of the plum blossoms to appear, very abundant, three-quarters of an inch in diameter; usually three springing from each flower-bud, often in dense clusters on lateral spurs and lateral buds on one-year-old wood; calyx-tube green, glabrous, campanulate or obconic; calyx-lobes acute to obtuse glandular-serrate, erect, glabrous or pubescent; petals white, oval, entire or crenate, with a short claw or tip; stamens about twenty-five, shorter than the petals; anthers yellow, sometimes tinged with red; pistils glabrous, longer than the stamens; pedicels one-half inch long, slender.
Fruit varying greatly in season, from very early to late; large, from one to two inches in diameter, globular, heart-shaped or often somewhat conical; cavity deep; apex conspicuously pointed; suture usually prominent; color varies greatly but usually a bright red or yellow, never blue or purple, lustrous, with little or no bloom; dots small, numerous, usually conspicuous; skin thin, tough, astringent; stem one-half inch in length; flesh red or more often yellow, firm, fibrous, juicy; quality variable, of distinct flavor, usually good; stone clinging tenaciously or nearly free, small, rough or lightly pitted, oval to ovate, one edge grooved, the other ridged.
A study of the botanical characters of the many Triflora plums under cultivation fails to show any lines of cleavage whereby the species can be divided. Of plums commonly grown in America it is not very closely related to any unless it be Prunus simonii. There are several plums from eastern and central Asia with which we are not at all familiar in America that may show relationship with Prunus triflora, chief of which are Prunus ichangana Schneider,[94] Prunus thibetica Franchet[95] and Prunus bokhariensis Royle,[96] the last a cultivated plum from northern India. These, in herbarium specimens, have some characters reminding one of Prunus triflora, others of Prunus domestica and still others, of Prunus cerasifera.
The Triflora, or Japanese,[97] plums are now cultivated in all parts of the world where plums are grown; yet outside of Japan and China they have been grown for their fruit less than half a century. Despite the fact that these plums have been grown in Asia for several centuries the wild form is not known. Indeed, there are doubts in the minds of some as to whether it constitutes a distinct species, Maximowicz, an authority on the flora of Japan, among others, holding that it is but a form of Prunus domestica. Roxburgh in naming it gave but little definite information in regard to the species, but the herbarium specimens of his in the Kew Herbarium are readily identified as identical with our Japanese plums.[98] The confusion between Prunus triflora and Prunus domestica seems needless, as the points of difference between these two species are several and very distinct and constant, the resemblances between Prunus triflora and some of the American species being much closer. So, too, the effort, sometimes made, to make more than one species out of Prunus triflora is straining a point, for though the types under cultivation vary considerably yet the variations are not greater than between varieties of other species of the genus Prunus.
Prunus triflora is almost certainly a native of China. According to Georgeson and Sargent, who have made extensive botanical explorations in the forests of Japan, there are no indigenous plum trees in that country. Dr. K. Miyake, botanist at the Agricultural College of the Imperial University, Tokyo, Japan, writes to this Station,[99] that Prunus triflora does not grow wild in Japan but was introduced there from China from two to four hundred years ago. Bretschneider[100] in his treatise on The Study and Value of Chinese Botanical Works says that the plum has been cultivated from ancient times in China and this indicates that the original habitat was in that country. Mr. F. N. Meyer, Agricultural Explorer for the United States Department of Agriculture, who has made extensive agricultural explorations in China, writes[101] that he has seen many trees of Prunus triflora cultivated in the Chekiang Province and also about Canton but that he had not found the species growing wild. Roxburgh says[102] that the shrub had been “received from China into our gardens in Bengal.” Forbes and Hemsley[103] state that varieties of this plum are cultivated in China and that it occurs in the wild state in the mountains near Peking as well as on the Tsunglin range in Shensi and Kansu. These writers are, however, uncertain as to where it is truly indigenous.
While the above and practically all evidence points to China as the original home of Prunus triflora it is likely that the habitat of the species cannot be accurately determined until western and southwestern China have been explored by botanists, these regions as yet being almost unknown to foreign scientists.