The family is especially abundant in E Asia, Europe, and North America, where species of almost half of the family's genera are indigenous, especially in the Pacific coastal area. Many of the Rosaceae are thorny, and most are characterized by the presence of stipules on the leaf, by flowers having five sets of parts, by a fleshy fruit, such as a rose hip or an apple, that is derived in large part from a cup-shaped enlargement of the flower stalk, and by the near absence of endosperm in the seed.
Although some groups of these plants are sometimes classed as separate families, most botanists consider them all to be a single family that represents a natural phylogenetic classification, i.e., most or all members have evolved from common ancestors. The largest of the approximately 110 genera (comprising a total of some 3,100 species) are Rubus (including the raspberry, blackberry, dewberry, loganberry, and other types of bramble), Spiraea (including the bridal wreath, meadowsweet, and hardhack), Rosa (the true roses), Crataegus (hawthorn), and Prunus (including the almond, apricot, blackthorn or sloe, cherry, nectarine, peach, and plum).
Economically the rose family is of enormous importance. It provides numerous temperate fruits including (besides species of Rubus and Prunus ) the apple, loquat, medlar, pear, quince, and strawberry. The typically fragrant and beautiful flowers make many members of the family prized as ornamentals, e.g., the fruit trees and bushes mentioned and also the antelope brush, Christmasberry, mountain ash, pyracantha, and shadbush. Many genera have species that are native wildflowers of the United States; in addition to many of those above are Agrimonia (agrimony), Potentilla (cinquefoil), and Sanguisorba (burnet), which are also sometimes cultivated.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.