The Hawthorn is the collective name of several hundred different species in the genus Crataegus. The Hawthorn is native to most temperate climates, but is sometimes introduced into colder and warmer climates.
The Hawthorn in the wild very rarely grows into a full fledged tree, usually growing in a more shrub or bush like pattern. However, certain varieties of Hawthorn are grown as ornamental trees, due to their brightly colored berries; and these varities usually grow into full fledged trees when tended correctly.
Most of what can be said about other members of the Rose family can be said of the Hawthorn. The plants are usually rather small, relativly short-lived, tend to tolerate cold climates, have small bisexual flowers that turn into bright red berries. They often propagate through asexual reproduction. And of course, as the name would suggest, they have thorns.
The Hawthorn is mostly distinguished from other members of the Rose family by their deeply notched, but not composite leaves, by the fact that they are usually even more shrublike then other members of the family, and by the fact that they sometimes produce berries with only one seed, especially in species such as monogyna.