About 450-500; see text

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Berberis thunbergii shoot with fruit

Berberis is a genus of about 450-500 species of deciduous and evergreen shrubs from 1-5 m tall with thorny shoots, native to the temperate and subtropical regions of Europe, Asia, Africa, North America and South America. They are closely related to the genus Mahonia, which is included within Berberis by some botanists. Many are known by the vernacular name barberry.

The genus is characterised by dimorphic shoots, with long shoots which form the structure of the plant, and short shoots only 1-2 mm long. The leaves on long shoots are non-photosynthetic, developed into three-spined thorns 3-30 mm long; the bud in the axil of each thorn-leaf then develops a short shoot with several normal, photosynthetic leaves. These leaves are 1-10 cm 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.

The deciduous species (e.g. Berberis thunbergii, B. vulgaris) are noted for good autumn colour, the leaves turning pink or red before falling. In some evergreen species from China (e.g. B. candidula, B. verruculosa), the leaves are brilliant white beneath, making them particularly attractive.

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 long, with six sepals and six petals in alternating whorls of three, the sepals usually coloured like the petals. The fruit is a small berry 5-15 mm long, ripening red or dark blue, often with a pink or violet waxy surface bloom; they may be either long and narrow (like a bar, hence 'barberry') or in other species, spherical. The berries are edible, and rich in vitamin C, though with a very sharp flavour; the thorny shrubs make harvesting them difficult, so they are not widely consumed. They are an important food for many small birds, which disperse the seeds in their droppings.

Several are popular garden shrubs, grown for their ornamental leaves, yellow flowers, and red or blue-black berries. They are also valued for crime prevention; being very dense, viciously spiny shrubs, they make very effective barriers impenetrable to burglars. For this reason they are often planted below potentially vulnerable windows, and used as hedges and other barriers.

Berberis vulgaris, the European Barberry, is the alternate host species of the wheat rust Puccinia graminis, a serious fungal disease of wheat. For this reason, cultivation of this species is prohibited in many areas.