They are shrubs and small trees growing to 5-15 m tall, characterized by their small pome fruit and thorny branches. The bark is smooth grey in young individuals, developing shallow longitudinal fissures with narrow ridges in older trees. The fruits are sometimes known as "haws", from which the name derived. The thorns grow from branches, and are typically 1-3 cm long. The leaves grow spirally arranged on long shoots, and in clusters on spur shoots on the branches or twigs. The leaves themselves have lobed or serrate margins and are somewhat variable shape.
The number of species in the genus depends on taxonomic interpretation, with numerous ; some botanists recognise a thousand or more species, while others reduce the number to 200 or fewer.
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 Lepidoptera species.
Many species and hybrids are used as and street trees. The Common Hawthorn is extensively used in Europe as a 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.
The fruits of the species ''Crataegus pinnatifida'' are tart, bright red, and resemble small fruits. They are used to make many kinds of Chinese snacks, including haw flakes and '''' . The fruits, which are called ''shānzhā'' in Chinese, are also used to produce jams, jellies, juices, alcoholic beverages, and other drinks . In South Korea, a liquor called ''sansachun'' is made from the fruits.To the western palate, drinks made from the fruits taste similar to barbecue sauce. and you can grind it up and smoke it
The fruits of ''Crataegus pubescens'' are known in Mexico as ''tejocotes'' and are eaten raw, cooked, or in jam during the winter months. They are stuffed in the ''pi?atas'' broken during the traditional pre-Christmas parties known as ''posadas''. They are also cooked with other fruits to prepare a Christmas punch. The mixture of ''tejocote'' paste, sugar, and chili powder produces a popular Mexican candy called ''rielitos'', which is manufactured by several brands.
In the southern United States fruits of three native species are collectively known as mayhaws and are made into jellies which are considered a great delicacy. In Canada, where hawthorns are strongly associated with the culture of Manitoulin Island, the fruits are commonly known as hawberries.
The leaves are edible and, if picked in the months of April and May, they are tender enough to be used in salads.
The dried fruits of ''Crataegus pinnatifida'' are used in naturopathic medicine and traditional Chinese medicine, primarily as a digestive aid. A closely related species, ''Crataegus cuneata'' is used in a similar manner. Other species are used in Western herbal medicine, where the plant is believed to strengthen cardiovascular function . In recent years, this use has been noted and adopted by Chinese herbalists as well . Hawthorn is also used as an aid to lower blood pressure, and treat some heart related diseases.
Several clinical trials have assessed the ability of hawthorn to help improve exercise tolerance in people with NYHA class II cardiac insufficiency compared to placebo. One trial, at for 4 to 8 weeks, found no difference from placebo. The second trial, including 78 subjects for 8 weeks, found "significant improvement in exercise tolerance" and lower blood pressure and heart rate during exercise. The third trial, including 32 subjects for 8 weeks, found improved exercise tolerance as well as a reduction in the "incidence and severity of symptoms such as dyspnea" and fatigue decreased by approximately 50% .
In the HERB-CHF clinical trial, 120 patients took 450mg of hawthorn extract twice daily for 6 months in combination with standard therapy and a standardized exercise program. "No effects of hawthorn were seen on either quality-of-life endpoint , or when adjusted for LVEF" .
One study, consisting of 1011 patients taking one tablet twice daily for 24 weeks, found "improvements in clinical symptoms , performance and exercise tolerance test, and ejection fraction" .
The wood of some hawthorn species is very hard and resistant to rot. In rural North America it was prized for use as tool handles and fence posts.
Overdose can cause cardiac arrhythmia and dangerously lower blood pressure. Milder side effects include nausea and sedation.
The custom of employing the flowering branches for decorative purposes on the 1st of 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. In the Scottish Highlands the flowers may be seen as late as the middle of June. The saying "Ne'er cast a cloot til Mey's oot" conveys a warning not to shed any before the summer has fully arrived and the may flowers are in full bloom.
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 gave rise doubtless to the tradition current among the French peasantry 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. Branches of , C. Oxyacantha, var. 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.
In Celtic lore, the hawthorn plant was used commonly for rune inscriptions along with and Apple. It was once said to heal the broken heart.
In Serbian folklore, a stake made of hawthorn wood was used to impale the corpses of suspected vampires.
During the seventies a facetious gardener working for the city of Vigo in Spain had a passion for grafting on common hawthorn. Onto seedlings of crataegus monogyna , he used to graft pink hawthorn, pear tree and medlar tree on the same trunk so the result was trees which gave pink and white flowers in May and fruits during the summer. He also performed chip budding grafts on hawthorn trunks in order to have several branches of several varieties on the same tree. He gave to these creations the name of sulcudus. Dozen of these trees have been planted in the various municipal gardens of the surrounding . Nowadays many of the sulcudus have disappeared, but it is still possible to admire a few specimens in the park of Pondevedra where in may the trees are all white and pink and in late August every passer by can pick nice ripe pears.
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