Crataegus (), commonly called hawthorn, quickthorn, thornapple, May-tree, whitethorn, Mayflower or hawberry, is a genus of several hundred species of shrubs and trees in the family Rosaceae, native to temperate regions of the Northern Hemisphere in Europe, Asia, North Africa and North America. The name "hawthorn" was originally applied to the species native to northern Europe, especially the common hawthorn C. monogyna, and the unmodified name is often so used in Britain and Ireland. The name is now also applied to the entire genus and to the related Asian genus Rhaphiolepis.
Etymology
The generic epithet, Crataegus, is derived from the Greek "strength" because of the great strength of the wood and "sharp", referring to the thorns of some species. The name haw, originally an Old English term for hedge (from the Anglo-Saxon term , "a fence with thorns"), also applies to the fruit.
Description
Crataegus species are shrubs or small trees, mostly growing to tall, with small pome fruit and (usually) thorny branches. The most common type of bark is smooth grey in young individuals, developing shallow longitudinal fissures with narrow ridges in older trees. The thorns are small sharp-tipped branches that arise either from other branches or from the trunk, and are typically long (recorded as up to in one case). The leaves grow spirally arranged on long shoots, and in clusters on spur shoots on the branches or twigs. The leaves of most species have lobed or serrated margins and are somewhat variable in shape. The fruit, sometimes known as a "haw", is berry-like but structurally a pome containing from one to five pyrenes that resemble the "stones" of plums, peaches, etc., which are drupaceous fruit in the same subfamily.
Taxonomy
The number of species in the genus depends on taxonomic interpretation. Some botanists in the past recognised 1000 or more species, many of which are apomictic microspecies. A reasonable number is estimated to be 200 species. The genus likely first appeared in the Eocene, with the ancestral area likely being Eastern North America and in Europe, which at that time remained closely linked due to the North Atlantic Land Bridge. The earliest known leaves of the genus from the Eocene of North America, with the earliest leaves from Europe being from the Oligocene.
The genus is classified into sections which are further divided into series. Series Montaninsulae has not yet been assigned to a section. The sections are: section Brevispinae section Crataegus section Coccineae section Cuneatae section Douglasia section Hupehensis section Macracanthae section Sanguineae