Shrub 0-3-l-5(-3) m tall, bushy, with branches spreading, sometimes weakly fron- dose. Stems reddish to orange, 4-lined or 4-angled when young, soon 2-lined, sometimes eventually terete; internodes 8-40 mm long, shorter than or rarely exceeding leaves; bark greyish-brown. Leaves petiolate, with petiole 0.5-2 mm long; lamina 15-60 x 5-30 mm, lanceolate or oblong-lanceolate to ovate or oblong-ovate, obtuse to rounded, always apiculate, margin plane, not incrassate, base narrowly or broadly cuneate to shortly angustate, rather glaucous beneath, chartaceous; venation: 3 pairs main laterals, with midrib branched distally and scarcely visible lax tertiary reticulum; laminar glands short streaks and dots; ventral glands ± dense. Inflorescence 1-15-flowered, from 1-2 nodes, corymbiform, sometimes with short apical internode, sometimes with 1-3-flowered branches from middle of stem; pedicels 2-4(-7) mm long; bracts narrowly elliptic to narrowly oblong, deciduous. Flowers 25-40 mm in diam., ± cyathiform; buds broadly ovoid, obtuse. Sepals 5-10 x 3.5-7 mm, free, ± imbricate, subequal or unequal, erect in bud and fruit, broadly ovate or broadly elliptic or subcircular to oblong-elliptic or obovate- spathulate, obtuse to rounded or retuse and usually apiculate, with margin finely eroded-denticulate to ciliolate, hyaline, often reddish; midrib often distinct, veins not or slightly prominent; laminar glands linear, numerous. Petals golden yellow, not tinged red, ± incurved, 12-18 x 10-14 mm, 1.5-2.5 x sepals, oblong-obovate to broadly obovate, with apiculus lateral, ± rounded to obsolete; margin entire or slightly eroded-denticulate, with a row of inframarginal gland dots. Stamen fascicles each with c. 50-70 stamens, longest 7-12 mm long, 0-4-0-5 x petals; anthers bright yellow. Ovary 5-6 x 3-5.4 mm, ± broadly ovoid; styles 4-5-5 mm long, 0.75-0.95 x ovary, ± erect, outcurved towards apex; stigmas not or scarcely capitate. Capsule 9-11 x 8-10 mm, broadly ovoid. Seeds dark brown, 1-1.2 mm long, ± cylindric, not or scarcely carinate, shallowly linear-foveolate. 2n = 36? (record is probably based on a misidentification, see Robson 1981: 150-151).
In dry, open habitats (thickets, scrubby slopes, cliffs); (300) 450-2400 m.
China (native in north Guizhou, Sichuan; probably introduced in other parts of China, certainly introduced in Taiwan, Japan, India and South Africa (Natal); specimens seen from Shaanxi, Jiangsu, Anhui, Zhejiang, Fujian, and Guangxi; also recorded from Hunan, Hubei, and Jiangxi).
H. patulum has a more northern distribution than H. henryi subsp. henryi, from which it can be distinguished by the more spreading habit, 2-lined stems, oblong- lanceolate to ovate rather than elliptic or ovate-lanceolate to ovate leaves, and usually by the smaller capsules. It was introduced to Britain from Nagasaki by Oldham in 1862 (Robson, 1970). H. patulum is less hardy in Europe than species such as H. pseudohenryi or H. forrestii. These species grow at higher altitudes than H. patulum and were introduced to cultivation later, when botanical collectors penetrated further into the mountainous regions of Yunnan and Szechwan. Most of them were at first regarded as 'improved', hardier versions of H. patulum, and were named as varieties of that species. However, they have all proved to be specifically distinct, and not even closely related to it.