- Name also: May Blossom, Oneseed Hawthorn, One-seed Hawthorn, Singleseed Hawthorn, Sigle-seeded Hawthorn
- Family: Rose Family – Rosaceae
- Growing form and height: Thorny shrub or tree. 3–6 m (10–20 ft.).
- Flower: Regular (actinomorphic), approx. 10 mm (0.4 in.) across. Calyx-lobes 5, broadly triangular, blunt, recurved, fine-hairy. Stamens 20. One carpel. Inflorescence a corymb, flower-stalks fine-hairy.
- Leaves: Stalked, broadly ovate, pinnately lobed. Lobes rounded, with entire margins but toothed at the tip, veins fine-hairy. Blade dull above, bluish-green beneath.
- Buds: Reddish-brown, egg-shaped.
- Fruit: An egg-shaped, red drupe, haw.
- Habitat: Broadleaf woods, coppices, scrubs. Rarely an ornamental.
- Flowering time: June.
- Endangerment: Critically endangered.
Hawthorns (Crataegus spp.) are a large and diverse genus. Especially the North American species are taxonomically difficult. Almost all species used as ornamentals belong to this group. The genus is also very old. In North America, fossils from the Cretaceous (140–170 mill. years ago) have been found.
Common hawthorn, also known as May blossom, belongs to the European and Central Asian group of approx. 100 species that are fairly easily distinguished. It often grows as a tree with a single trunk. The smell of its flowers is unpleasant. The berries are edible. Common hawthorn has also been used as a medicinal plant.
At first glance calycine hawthorn can be difficult to tell apart from common hawthorn. With closer look flowers are larger, leaves have narrower apexes and leave margins are sharper-toothed. Also stipules are toothed (entire with common hawthorn). This species is classified as endangered.
NOT TRANSLATED YET. Midland hawthorn (English hawthorn, Woodland hawthorn) on kohtalaisen harvinainen laji Suomessa, lähinnä puutarhapensas, joskus karkulainen. Se muistuttaa tylppöorapihlajaa. Lehdet ovat harvempi- ja pyöreämpiliuskaiset ja liuskat ovat melko matalahampaiset. Marja on 2-siemeninen. Kaikki tällä sivulla kuvatut orapihlajat risteytyvät melko yleisesti keskenään, joten voi olla lähes mahdotonta kertoa takuuvarmasti, mistä lajista tai risteymästä on kysymys.