Berberidaceae is well represented in the northern temperate zones with 15 genera, and about 650 species, most of which are in the genus Berberis. They are mostly shrubby plants, sometimes with a rhizomatous root system. Leaves can be single or compound, venation pinnate or palmate. Flowers are pollinated by insects; the stamens are loosely attached to the bottom of flowers and springing up violently as they are disturbed. This mechanism ensures that the visiting insects are dusted with pollen. Berries of some members of the family such as Berberis spp. barberry) and Mahonia aquifolium (Oregon grape) are edible.