Crataegus (/krəˈtiːɡəs/),[2] commonly called hawthorn, quickthorn,[3] thornapple,[4] May-tree,[5] whitethorn,[5] Mayflower or hawberry, is a genus of several hundred species of shrubs and trees in the family Rosaceae,[6] native to temperate regions of the Northern Hemisphere in Europe, Asia, North Africa and North America.

The most common type of bark is smooth grey in young individuals, developing shallow longitudinal fissures with narrow ridges in older trees.

[8] Flowers are five-petalled and grow in flat-topped clusters and are most typically white, although they can also be pale pink or occasionally scarlet in colour.

[22] Hawthorns are also used as food plants by the larvae of a large number of Lepidoptera species, such as the small eggar moth, E.

[27] In the southern United States, fruits of three native species are collectively known as mayhaws and are made into jellies which are considered a delicacy.

The mixture of tejocote paste, sugar and chili powder produces a popular Mexican candy called rielitos, which is manufactured by several brands.

[29] A 2008 Cochrane Collaboration meta-analysis of previous studies concluded that evidence exists of "a significant benefit in symptom control and physiologic outcomes" for an extract of hawthorn used as an adjuvant in treating chronic heart failure.

[30] A 2010 review[31] concluded that "Crataegus [hawthorn] preparations hold significant potential as a useful remedy in the treatment of cardiovascular disease".

The review indicated the need for further study of the best dosages and concluded that although "many different theoretical interactions between Crataegus and orthodox medications have been postulated ... none have [yet] been substantiated.

The products used are often derived from C. monogyna, C. laevigata, or related Crataegus species, sometimes generally referred to as hawthorn without distinguishment.

[34] Overdose can cause cardiac arrhythmia and low blood pressure, while milder side effects include nausea and dizziness.

During the British Agricultural Revolution in the eighteenth and nineteenth centuries, hawthorn saplings were mass propagated in nurseries to create the new field boundaries required by the Inclosure Acts.

It is graft-compatible with Mespilus (medlar) and with pear,[8] and makes a hardier rootstock than quince, but the thorny suckering habit of the hawthorn can be problematic.

[21] The Scots saying "Ne'er cast a cloot til Mey's oot" conveys a warning not to shed any (clothes) before the summer has fully arrived and the mayflowers (hawthorn blossoms) are in full bloom.

[40][41] The custom of employing the flowering branches for decorative purposes on 1 May is of very early origin, but since the adoption of the Gregorian calendar in 1752, the tree has rarely been in full bloom in England before the second week of that month.

The hawthorn has been regarded as the emblem of hope, and its branches are stated to have been carried by the ancient Greeks in wedding processions, and to have been used by them to deck the altar of Hymenaios.

The supposition that the tree was the source of Jesus's crown of thorns doubtless gave rise to the tradition among the French peasantry (current as late as 1911) that it utters groans and cries on Good Friday, and probably also to the old popular superstition in Great Britain and Ireland that ill luck attended the uprooting of hawthorns.

praecox), which flowers both in December and in spring, were formerly highly valued in England, on account of the legend that the tree was originally the staff of Joseph of Arimathea.

[42] Robert Graves, in his book The White Goddess,[5] traces and reinterprets many European legends and myths in which the whitethorn (hawthorn), also called the May-tree, is central.

[45] This warning persists to modern times; folklorist Bob Curran has questioned whether the ill luck of the DeLorean Motor Company was associated with the destruction of a fairy thorn to make way for a production facility.

Since the reign of King James I, it has been a Christmas custom to send a sprig of Glastonbury thorn flowers to the Sovereign, which is used to decorate the royal family's dinner table.