Plum
2 of the 6 encyclopedias on this shelf carry an entry for Plum. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a fruit-bearing shrub akin to the peach, almond, and cherry. It is pretty difficult to classify plums. Of native plums we have the common wild plum of the North, the Chickasaw plum of the South, the sand plum of the plains, the beach plum of the Atlantic coast, and the Pacific plum. Of plums introduced we have the apricot plum from China, Japanese plums, cherry plums, and domestic plums from Europe. Prunes are sweet plums that may be dried on the pit without fermentation or souring. Damsons and green gages are well known plum types. As in the case of apples, plum trees are propagated by planting seeds, grafting, and seedlings. Some nurserymen graft plum twigs on peach seedlings. California is our chief plum-producing state. Freedom from insect plagues, with soil and climate unsurpassed, has brought the state forward to a prune production of 337,000,000 pounds in 1900, not including canned plums and enormous shipments of crated green fruit. Plum blossoms appear in early spring before the leaves. They rival apple blossoms in fragrance. On account of their hardiness, plum trees are raised probably in more dooryards than any other fruit tree. The real way to enjoy plums, however, is to find wild plums in the woods and eat them before going home. See Prunes
Collier's New Encyclopedia (1921)
the fruit of sub-species of P. the common plum, a tree itself. It is a communis or that and Asia Minor, native of the Caucasus it was introduced into Europe at a very early period. It has run into varieties. more than 300
What Has Changed in the Last Century
The botany in both entries still holds: plums remain close kin to peaches, almonds and cherries, the European domestica plums trace to the Caucasus region, and the tangle of native American species Aiton lists — wild, Chickasaw, sand, beach and Pacific plums — is still recognised. What has moved is the trade. Aiton's boast of California's 337,000,000 pounds of prunes and "freedom from insect plagues" reads oddly now: China grows more than half the world's plums, and in 2000 the US industry won permission to sell prunes as "dried plums" to shake off the fruit's laxative reputation. Plum pox virus, the disease growers most fear, reached North America in the 1990s and prompted a genetically engineered resistant plum, HoneySweet, cleared by US regulators in the 2000s; nurserymen also now graft mostly onto Myrobalan-type plum rootstocks rather than the peach seedlings Aiton mentions.
Written for this edition, 2026.