Holly (Ilex) is a genus of about 600 species of flowering plants in the familyAquifoliaceae, and the only living genus in that family. One other genus, the monotypicNemopanthus (Mountain Holly), was formerly separated from Ilex on the basis that its flowers have a reduced calyx and narrow petals, and also in cytology, being tetraploid, whereas Ilex is diploid. However, following analysis of molecular data, Mountain Holly has now been merged into Ilex, as I. mucronata; it is closely related to I. amelanchier.[1][2]
Hollies (here, Ilex aquifolium) are dioecious: (above) shoot with flowers from male plant; (top right) male flower enlarged, showing stamens with pollen and reduced, sterile stigma; (below) shoot with flowers from female plant; (lower right) female flower enlarged, showing stigma and reduced, sterile stamens with no pollen.
Hollies are shrubs and trees from 2?25 m tall, with a wide distribution in Asia, Europe, Africa, and North and South America. Most species are found in the tropics and subtropics of America and Asia - China has 204 native species[3] - but this account is based largely on the well-studied species of Europe and North America. The leaves are simple, and can be either deciduous or evergreen depending on the species, and may be entire, finely toothed, or with widely-spaced, spine-tipped serrations. They are mostly dioecious, with male and female flowers on different plants, with some exceptions. Pollination is mainly by bees and other insects. The fruits are small drupes, usually with four to six pits, and range in color from red to purple-black.[4] One species in China, Ilex chapaensis, has large green fruits that are eaten by civets[5].
A holly bush with a lone red berry in winter.
Holly berries are mildly toxic and will cause vomiting and/or diarrhea when ingested by people. However they are extremely important food for numerous species of birds, and also are eaten by other wild animals. In the fall and early winter the berries are hard and apparently unpalatable. After being frozen or frosted several times, the berries soften, and become milder in taste. During winter storms, birds often take refuge in hollies, which provide shelter, protection from predators (by the spiny leaves), and food. The flowers are sometimes eaten by the larva of the Double-striped Pugmoth (Gymnoscelis rufifasciata). Other Lepidoptera whose larvae feed on holly include Bucculatrix ilecella (which feeds exclusively on hollies) and The Engrailed (Ectropis crepuscularia). The Japanese Beetle (Popillia japonica) is another well-known animal feeding on holly leaves. Holly is commonly referenced at Christmas time.
Having evolved numerous species that are endemic to islands and small mountain ranges, and being highly useful plants, many hollies are now becoming rare. Tropical species are especially often threatened by habitat destruction and overexploitation, and at least two have become extinct, with numerous others barely surviving.[6]
The botanical name ilex was the original Latin name for the Holm Oak (Quercus ilex), which has similar foliage to common holly, and is occasionally confused with it.
In many western cultures, holly is a traditional Christmas decoration, used especially in wreaths. The wood is heavy, hard and whitish; one traditional use is for chess pieces, with holly for the white pieces, and ebony for the black. Other uses include turnery, inlay work and as firewood. Looms in the 1800s used holly for the spinning rod. Because holly is dense and can be sanded very smooth, the rod was less likely than other woods to snag threads being used to make cloth.
Many of the hollies are widely used as ornamental plants in gardens and parks. Several hybrids and numerous cultivars have been developed for garden use, among them the very popular Ilex × altaclerensis (I. aquifolium × I. perado) and Ilex × meserveae (I. aquifolium × I. rugosa).[8] Hollies are often used for hedges; the spiny leaves make them difficult to penetrate, and they take well to pruning and shaping. [9] In Heraldry, holly is used to symbolise truth.
Between the thirteenth and eighteenth century, before the introduction of turnips, holly was cultivated for use as winter fodder for cattle and sheep.[10] Less spiny varieties of holly were preferred, and in practice the leaves growing near the top of the tree have far fewer spines making them more suitable for fodder.
Several holly species are used to make caffeine-rich herbal teas. The South AmericanYerba Mate (I. paraguariensis) is boiled for the popular revigorating drinks Mate, and Chimarrăo, and steeped in water for the cold Tereré. Guayusa (I. guayusa) is used both as a stimulant and as an admixture to the entheogenic tea ayahuasca; its leaves have the highest known caffeine content of any plant. In North and Central America, Yaupon (I. vomitoria), was used by southeastern Native Americans as a ceremonial stimulant and emetic known as "the black drink"[11]. As the name suggests, the tea's purgative properties were one of its main uses, most often ritually. Evergreen Winterberry (Appalachian Tea, I. glabra) is a milder substitute for Yaupon. In China, the young leaf buds of I. kudingcha are processed in a method similar to green tea to make a tisane called k?d?ng chá (???, roughly "bitter spikeleaf tea").
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