Apples, almonds and strawberries all belong to the rose family
A fruit bowl holding an apple, a peach, a cherry and a handful of raspberries is really a family reunion. All belong to the Rosaceae, along with almonds, pears, apricots and the roses themselves. Their flowers share a tell-tale cup at the base, and almost none of them are ever blue.
The family counts 4,828 known species in 91 genera, named after its type genus, Rosa. Members range from trees and shrubs to climbers and herbs and grow worldwide, though they are most diverse in the Northern Hemisphere. Prunus alone holds some 340 species, among them plums, peaches and almonds, and ornamentals such as rowans and firethorns round out the list.
The flowers are showy, symmetrical and nearly always contain both male and female parts, typically with five sepals, five petals and many stamens. Their bases fuse into a cup called a hypanthium. Petals come in many colours, but blue is almost entirely missing.
What makes the family so useful at the table is the variety of its fruits. Cherries and plums are drupes with a stone; an apple is a pome, whose flesh comes largely from tissue around the ovary; a rose hip is another accessory fruit; and a strawberry's juicy part is the swollen receptacle, dotted with tiny true fruits. Botanists once used these fruit types to carve up the family, a division now considered artificial. Many seeds contain amygdalin, which can release cyanide if the seed is crushed during digestion.
Counting species is harder than it sounds. Several genera reproduce by apomixis, setting seed without fertilisation, which produces swarms of near-identical forms that resist tidy division. Hawthorns may number anywhere from 200 to 1,000 species, and brambles run to hundreds or possibly thousands. Classification has shifted repeatedly, from six traditional subfamilies to today's scheme of three, with the apple lineage folded into a broader subfamily to keep the groups natural.
Source: Rosaceae
