Mahonia
Mahonia is a genus of approximately 70 species of evergreen shrubs and, rarely, small trees in the family Berberidaceae, native to eastern Asia, the Himalaya, North and Central America. They are closely related to the genus "Berberis" and botanists disagree on whether to recognize a separate "Mahonia". Many botanists prefer to classify "Mahonia" as a part of "Berberis" because several species in both genera are able to hybridize, and because there are no consistent morphological 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 and are termed "unifoliolate"; additionally their branched spines are modified compound leaves). However, recent DNA-based phylogenetic studies retain 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 are then divided into three genera: "Mahonia", "Alloberberis" (formerly "Mahonia" section "Horridae"), and "Moranothamnus" (formerly "Berberis claireae"); a broadly-circumscribed "Berberis" (that is, including "Mahonia", "Alloberberis", and "Moranothamnus") would also be monophyletic. "Mahonia" species bear pinnate leaves long with 3 to 15 leaflets, and flowers in racemes which are long. Several species  are popular garden shrubs, grown for their ornamental, often spiny, evergreen foliage, yellow (or rarely red) flowers in autumn, winter and early spring, and blue-black berries. The flowers are borne in terminal clusters or spreading racemes, and may be among the earliest flowers to appear in the growing season. The ripened fruits are acidic with a very sharp flavor. The plants contain berberine, a compound found in many "Berberis" and "Mahonia" cause vomiting, lowered blood pressure, reduced heart rate, lethargy, and other ill effects when consumed. The genus name, "Mahonia", derives from Bernard McMahon, one of the stewards of  the plant collections from the Lewis and Clark expedition. The type species of the genus is "M. aquifolium". Species. The following list includes all currently recognized species of the genus "Mahonia" as accepted by Tropicos, Missouri Botanical Garden as of February 2016, sorted alphabetically. For each, binomial name is followed by author citation. Diseases. Some "Mahonia" species serve as alternate hosts for the cereal disease stem rust (Puccinia graminis).