Many-stemmed shrub to 7 m, rarely a small tree. Bark grey. Twigs with a moderately dense brownish pubescence and longer gland-tipped hairs. Leaf 4–13 × 3–10 cm, elliptic to suborbicular (rarely more obovate), base cordate, top rounded either side of an abruptly pointed mucronate tip, margin irregularly doubly serrate and usually lobulate, pubescent at least under the veins; petiole 1–2(–3) cm, sparsely pubescent. Male catkins in clusters of 2–5. Nuts in clusters of 2–6, ovoid to globose, to 15 mm wide; bracts campanulate and scarcely longer than the nut, spreading to reveal its upper portion, their margin with usually dentate triangular lobes, longitudinally ridged, densely pubescent and with stiff glandular hairs near the base (Li & Skvortsov 1999).
Distribution China Anhui, S Gansu, Guizhou, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Shandong, NE Sichuan (Chengkou Xian), Zhejiang.
Habitat Thickets on moist, warm mountainsides, to 2500 m.
USDA Hardiness Zone 5
RHS Hardiness Rating H6
Conservation status Data deficient (DD)
Taxonomic note The epithet for this taxon was published as Corylus heterophylla var. sutchuenensis Franch. (1899). When elevated to specific rank by Nakai in the Journal of Japanese Botany (1939) the epithet appeared as C. sutchuensis (Franch.) Nakai, almost certainly as a typographic error since Franchet is cited as the author of the basionym. Such orthographic errors are regarded as correctable in Art. 60 of the International Code of Nomenclature for algae, fungi, and plants and following the lead of Plants of the World Online we adopt the spelling Corylus sutchuenensis here (athough see below). (Nakai’s misprint does seem to have contributed to Franchet’s original combination in C. heterophylla appearing more often than not in contemporary literature as ‘sutchuensis’, while it is also mis-spelled as ‘sutchuanensis’ in Flora of China.) Corylus sutchuenensis is treated by Plants of the World Online (Royal Botanic Gardens, Kew 2023), whose nomenclature is followed elsewhere in this account, as a variety of C. heterophylla (var. sutchuenensis Franch.). However, a recent phylogenetic analysis (Zhao et al. 2020) shows the population from southern China to be clearly distinct from C. heterophylla and closer to C. yunnanensis. In Zhao et al., this population is called C. kweichowensis; the authors follow authorities such as POWO, Flora of China (Li & Skvortsov 1999) and Holstein, Tamer & Weigend (2018) in treating this taxon as synonymous with C. heterophylla var. sutchuenensis; but at specific rank C. sutchuenensis (Franch.) Nakai (1939) has priority over C. kweichowensis Hu (1948). Flora Sichuanica takes a slightly different approach and follows Liang (1988) in treating sutchuensis (sic) as a variety of Hu’s broader species C. kweichowensis (Yang 2012), along with var. brevipes Liang. A further issue to complicate this situation is the existence of two more taxa accepted by POWO but not mentioned by Flora of China, even as synonyms: C. potaninii, described in 1936 by Alexey Bobrov in relation to C. heterophylla var. sutchuenensis (and to C. heterophylla var. crista-galli Burkill, which Bobrov seems to have understood as a different variant again), and C. wulingensis Q.X. Liu & C.M. Zhang, described in 1990 as a species intermediate between C. yunnanensis and C. heterophylla var. crista-galli. Further research into this group is clearly required.
As the taxonomic note suggests, the hazels which take the place of Corylus heterophylla (var. heterophylla) in the warmer mountain forests across the south of China are probably quite variable, but also distinct enough as an entire population for species status to be appropriate. Their leaves lack the very abruptly truncate tops which are an often characteristic feature of the northern heterophylla, and the lobes of their nuts’ husks usually have rounded teeth along them, rather than being entire.
Nomenclatural instability has doubtless resulted in these hazels being even more obscure in cultivation in the west than they might have been, but they are probably better adapted to western Europe than C. heterophylla itself. In the colder, continental climate of Lansing, Michigan (North American Climate Zone 5b), the amateur hazelnut breeder Cecil Farris obtained one plant from western China, which he was able to keep alive, using pollen from a hazel of European breeding to produce the ‘Estrella’ series of hybrids in the 1970s (Molnar 2011; see further under Corylus avellana × sutchuenensis). This may not, however, have represented the first introduction to the west, since one plant at the Holden Arboretum in Ohio has a 1954 accession date (Royal Botanic Garden Edinburgh 2023). An example at the Arnold Arboretum in Massachusetts was grown from seed from Zhejiang Province in 1989 (Friedman 2022). In the UK, a small bush at the Sir Harold Hillier Gardens was accessioned in 1983 (Royal Botanic Garden Edinburgh 2023), while H&M 2008 and Mason 10 are represented at Howick Hall in Northumberland (Howick Hall Arboretum 2023). GUIZ 4, collected in October 1985 on a scrub-covered limestone hillside 18 km from Guiyang, Guizhou, since grown at the Yorkshire Arboretum as ‘Corylus sp.’ also presumably belongs here. Its nuts have not been observed in cultivation, but the field note states ‘nuts in large frilly bracts, exceeding seed considerably.’