Berberis

Berberis (), commonly known as barberry, is a large genus of deciduous and evergreen shrubs from 1-5 m (3.3-16.4 ft) tall, found throughout temperate and subtropical regions of the world (apart from Australia). South America and Asia have the greatest diversity of species. However, North America, Europe and Africa all have native species. The most well-known Berberis is the European barberry, Berberis vulgaris. It is found in Europe, North Africa and the Middle East. It has also been introduced to North America. Many of the species have spines on the shoots and all along the margins of the leaves.

Description

The genus Berberis has dimorphic shoots: long shoots which form the structure of the plant, and short shoots only 1-2 mm (0.039-0.079 in) long. The leaves on long shoots are non-photosynthetic, developed into one to three or more spines^:96 3-30 mm (0.12-1.18 in) long. Each thorn-leaf’s bud develops a shorter shoot with several photosynthetic normal leaves. These leaves are 1-10 cm (0.39-3.94 in) long, simple, and either entire, or with spiny margins. Only on young seedlings do leaves develop on the long shoots, with the adult foliage style developing after the young plant is 1-2 years old.^{[citation needed]}

Many deciduous species, such as Berberis thunbergii and B. vulgaris, are noted for their attractive pink or red autumn color. In some evergreen species from China, such as B. candidula and B. verruculosa, the leaves are brilliant white beneath, a feature valued horticulturally. Some horticultural variants of B. thunbergii have dark red to violet foliage.^{[citation needed]}

The flowers are produced singly or in racemes of up to 20 on a single flower-head. They are yellow or orange, 3-6 mm (0.12-0.24 in) long, sepals are usually six, rarely three or nine and there are six petals in alternating whorls of three, the sepals usually colored like the petals. The fruit is a small berry 5-15 mm (0.20-0.59 in) long, ripening red or dark blue, often with a pink or violet waxy surface bloom; in some species, they may be long and narrow, but are spherical in other species.^{[citation needed]}

Some authors consider the compound-leaved species to be part of a different genus, Mahonia. There are no consistent differences between the two groups other than the leaf pinnation (Berberis sensu stricto appear to have simple leaves, but these are in reality compound with a single leaflet; they are termed “unifoliolate”), and many botanists prefer to classify all these plants in the single genus Berberis. However, a recent DNA-based phylogenetic study retains the two separate genera, by clarifying that unifoliolate-leaved Berberis s.s. is derived from within a paraphyletic group of shrubs bearing imparipinnate evergreen leaves, which the paper then divides into three genera: Mahonia, Alloberberis (formerly Mahonia section Horridae), and Moranothamnus (formerly Berberis claireae); it confirms that a broadly-circumscribed Berberis (that is, including Mahonia, Alloberberis, and Moranothamnus) is monophyletic.

Cultivation

Several species of Berberis are popular garden shrubs, grown for such features as ornamental leaves, yellow flowers, or red or blue-black berries. Numerous cultivars and hybrids have been selected for garden use. Low-growing Berberis plants are also commonly planted as pedestrian barriers. Taller-growing species are valued for crime prevention; being dense and viciously spiny, they are effective barriers to burglars. Thus they are often planted below vulnerable windows, and used as hedges. Many species are resistant against predation from deer.

Species in cultivation include:

The following hybrid selections have gained the Royal Horticultural Society’s Award of Garden Merit:

Ecology

Berberis species are used as food plants by the larvae of some Lepidoptera species, including the moths barberry carpet moth (Pareulype berberata), and mottled pug (Eupithecia exiguata).^{[citation needed]}

Berberis can infect wheat with root rust, a serious fungal infection of wheat and other related grains. Berberis vulgaris (European barberry) and Berberis canadensis (American barberry) serve as alternate host species of the rust fungus responsible, the wheat rust fungus (Puccinia graminis). For this reason, cultivation of B. vulgaris is prohibited in many areas, and imports to the United States are forbidden. The North American B. canadensis, native to Appalachia and the Midwest United States, was nearly eradicated for this reason, and is now rarely seen extant, with the most remaining occurrences in the Virginia mountains.^{[citation needed]}

Some Berberis species have become invasive when planted outside of their native ranges, including B. glaucocarpa and B. darwinii in New Zealand (where it is now banned from sale and propagation), and B. vulgaris and green-leaved B. thunbergii in much of the eastern United States.^{[citation needed]}

In 32 US states, Japanese barberry is an invasive species. It is deer resistant because of its taste and is favored as a shelter for ticks that can carry lyme disease.