Rosaceae

Rosaceae (/roʊˈzeɪsiː.iː, -si.aɪ, -si.eɪ/), the rose family, is a family of flowering plants that includes 4,828 known species in 91 genera.

The name is derived from the type genus Rosa. The family includes herbs, shrubs, and trees. Most species are deciduous, but some are evergreen. They have a worldwide range but are most diverse in the Northern Hemisphere.

Many economically important products come from the Rosaceae, including various edible fruits, such as apples, pears, quinces, apricots, plums, cherries, peaches, raspberries, blackberries, loquats, strawberries, rose hips, hawthorns, and almonds. The family also includes popular ornamental trees and shrubs, such as roses, meadowsweets, rowans, firethorns, and photinias.

Among the most species-rich genera in the family are Alchemilla (270), Sorbus (260), Crataegus (260), Cotoneaster (260), Rubus (250), and Prunus (340), which contains the plums, cherries, peaches, apricots, and almonds. However, all of these numbers should be seen as estimates—much taxonomic work remains.

Rosaceae can be woody trees, shrubs, climbers or herbaceous plants. The herbs are mostly perennials, but some annuals also exist, such as Aphanes arvensis.

The leaves are generally arranged spirally, but have an opposite arrangement in some species. They can be simple or pinnately compound (either odd- or even-pinnate). Compound leaves appear in around 30 genera. The leaf margin is most often serrate. Paired stipules are generally present and are considered a primitive feature within the family, though they have been independently lost in many groups of Amygdaloideae (previously called Spiraeoideae). The stipules are sometimes adnate (attached surface to surface) to the petiole. Glands or extrafloral nectaries may be present on leaf margins or petioles. Spines may be present on the midrib of leaflets and the rachis of compound leaves.

Flowers of plants in the rose family are generally described as "showy". They are radially symmetrical, and almost always hermaphroditic. Rosaceae generally have five sepals, five petals, and many spirally arranged stamens. The bases of the sepals, petals, and stamens are fused together to form a characteristic cup-like structure called a hypanthium. They can be arranged in spikes, or heads. Solitary flowers are rare. Rosaceae have a variety of color petals, but blue is almost completely absent.

The fruits occur in many varieties and were once considered the main characters for the definition of subfamilies amongst Rosaceae, giving rise to a fundamentally artificial subdivision. They can be follicles, capsules, nuts, achenes, drupes (Prunus), and accessory fruits, like the pome of an apple, the hip of a rose, or the receptacle-derived aggregate accessory fruit of a strawberry. Many fruits of the family are edible, but their seeds often contain amygdalin, which can release cyanide during digestion if the seed is damaged.