Erect shrub to 3m or so tall. Leaves about 30-40 cm long. Leaflets mostly 9-11, more or less ovate, very tough and with few spines (less than 10), pale green, tips long-pointed, bases rounded. Flowers in long, lax clusters about 15-35 cm long, fragrant; winter and early spring. Fruits 6-7 mm wide, dark blue.
M. japonica (Thunb.) DC. has 13-19 leaflets per leaf. South-eastern Australian plants sold under this name consistently produce 9 leaflets (rarely more) and long flower clusters to 35 cm long (not 25 cm) indicating possible hybridisation. This species was originally named from plants cultivated in Japan which accounts for the apparent contradiction between the specific epithet and its natural distribution.
M. bealei (Fortune) Carrière is the name given to a Chinese variant of the species probably rating cultivar status only as M. japonica 'Bealei': it has broader leaflets about 4 cm wide with the terminal leaflet not narrowed, and erect, dense flower spikes.
Source: (1997). Berberidaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press. (as Mahonia aff. japonica)