Crataegus ( //), commonly called hawthorn or thornapple, is a large genus of shrubs and trees in the rose family, Rosaceae, native to temperate regions of the Northern Hemisphere in Europe, Asia 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. However the name is now also applied to the entire genus, and also to the related Asian genus Rhaphiolepis.
They are shrubs or small trees, mostly growing to 5–15 metres (16–49 ft) 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 1–3 cm long (recorded as up to 11.5 centimetres (4.5 in) 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 serrate margins and are somewhat variable in shape. The fruit, sometimes known as a "haw", is berry-like, but structurally a pome containing from 1 to 5 pyrenes that resemble the "stones" of plums, peaches, etc. which are drupaceous fruit in the same subfamily.
Hawthorns provide food and shelter for many species of birds and mammals, and the flowers are important for many nectar-feeding insects. Hawthorns are also used as food plants by the larvae of a large number of Lepidoptera species; see List of Lepidoptera that feed on hawthorns. Haws are important for wildlife in winter, particularly thrushes and waxwings; these birds eat the haws and disperse the seeds in their droppings.
Many species and hybrids are used as ornamental and street trees. The Common Hawthorn is extensively used in Europe as a hedge plant. Several cultivars of the Midland Hawthorn C. laevigata have been selected for their pink or red flowers. Hawthorns are among the trees most recommended for water conservation landscapes.