The evolution in varieties and species of plums grown in the United States and Canada during the past thirty years is quite as remarkable as the development of the strawberry and grape during that period. The second edition of Charles Downing's great work on American fruits, including his third appendix, describes about three hundred varieties of the plum, all of the Domestica class except the Wild Goose, Miner, and Newman. No mention is made of the Japan varieties, and the American species are only referred to in the foot-note: " There are three species of wild plum indigenous to this country, of tolerable flavor but seldom cultivated in our gardens." Bulletin No. 8 of the Division of Pomology of the Department of Agriculture indicates some of the changes of a few years. This Bulletin, published in 1899, includes and describes twenty-two varieties of Prunus Americana, eight of Prunus angustifolia, eighteen of Prunus hortulana, two of Prunus cerasifera, seventeen of Primus triflora, seven of Prunus pumila, and over sixty of Prunus domestica, and this includes a number of varieties developed by Burbank and others by crossing with native varieties, and it also includes the leading varieties of plums and prunes grown in California and Oregon.
Prof. F. A. Waugh, in his valuable book on "Plums and Plum Culture," divides the native varieties into several groups or sub-species. Prunus chicasa of Asa Gray is separated into the Miner-like group, the Wayland-like group, the Wildgoose group, and the Chicasaw group, and the northern species, Prunus Americana, is divided into two groups - the Americana and Nigra.
This minute division cannot be made accurate, and is confusing to amateur growers and those not familiar with botanical descriptions.
At this time it will be best for the purposes of this publication to follow the classification given by Prof. Bailey as follows : (I) Prunus domestica, which includes the garden plums and prunes of European origin and their hybrids; (2) Prunus triflora, which includes the newly introduced varieties from Japan, their seedlings and hybrids; (3) Prunus Americana, including the native varieties of the North; (4) Prunus angustifolia, including the Southern types of chicasa; (5) Prunus hortulana, including the Wildgoose group and the Miner-like varieties, extending farthest north; (6) the hybrid varieties and those not easy to classify.
As far as possible varieties no longer cultivated are omitted, and where possible the relative hardiness of varieties will be indicated.
For facts pertaining to propagation, cultivation, pruning, and management, see index of Part I.
The figures outlining the general forms of plums are copied from Downing, and will prove some aid to beginners in understanding the descriptions.
(To face page 293.)