|Flowers of Mahonia oiwakensis|
Mahonia oiwakensis is a species of plant in the barberry family, Berberidaceae. It is native to China (Taiwan, Guizhou, Hong Kong, Sichuan, Taiwan, Xizang (Tibet) and Yunnan) and Myanmar, where it occurs at elevations of 600 to 3800 m. It has recently been found naturalized in South Africa.
This species has long been known by the name Mahonia lomariifolia, published by Takeda in 1917. Under that name, it was considered to occur only in mainland China, while on Taiwan, a second species was found, known as M. oiwakensis. Modern taxonomic sources unite the two as a single species, but as the latter name was published a year earlier by Hayata, it has priority and is thus the accepted name. In recognition of the morphological differences between the Taiwanese and mainland Chinese plants, Shaw recognized the two as subspecies of Mahonia oiwakensis: M. oiwakensis subsp. oiwakensis in Taiwan and M. oiwakensis subsp. lomariifolia in mainland China. In addition, a plant collected in Yunnan with especially narrow leaflets was described as a new variety: Mahonia oiwakensis subsp. lomariifolia var. tenuifoliola.
Mahonia oiwakensis is a shrub or tree up to 7 m tall. Leaves are up to 45 cm long, compound with 12-20 pairs of leaflets plus a larger terminal one, dark green above, yellow-green below. The inflorescence is a fascicled raceme up to 25 cm long. The berries are egg-shaped, dark blue, sometimes almost black, up to 8 mm long.
Mahonia oiwakensis subsp. lomariifolia is one parent of the important garden hybrid Mahonia x media, which includes popular cultivars such as 'Charity', 'Winter Sun' and 'Lionel Fortescue' (the other parent is Mahonia japonica). It is also a parent of the cultivar 'Arthur Menzies', though with Mahonia bealei as the other parent. In the wild in Taiwan, M. oiwakensis subsp. oiwakensis appears to hybridize with wild Mahonia japonica.
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- Takeda, Hisayoshi (1917). "Contributions to the Knowledge of the Old World Species of the Genus Mahonia". Notes from the Royal Botanic Garden, Edinburgh. 6 (29–30): 209–248 – via Biodiversity Heritage Library.
- Hayata, Bunzo (1916). "Contributions to the Flora of Formosa". Icones plantarum formosanarum nec non et contributiones ad floram formosanam. 6: 1–163 – via Biodiversity Heritage Library.
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