Oaks of the World

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  Quercus langbianensis
Author Hickel & A.Camus 1921 Ann. Sci. Nat., Bot. X, 3: 382
Synonyms baniensis A.Camus 1936 (A. Camus : n 28)
blaoensis A.Camus 1935 (A. Camus : n 27)
cambodiensis Hick. & A.Camus 1923 (A. Camus : n 10)
langbianensis subsp cambodiensis (Hickel & A. Camus) Menitsky 1976
camusiae Trel. ex Hickel & A.Camus 1929 (A. Camus n 25)
Cyclobalanopsis camusiae (Trel. ex Hickel & A.Camus) Y.C. Hsu & H.W. Jen 1993
pachyloma var. mubianensis Y.C. Hsu & H.W. Jen 1976
Cyclobalanopsis pachyloma var. mubianensis (Y.C. Hsu & H.W. Jen) C.C. Huang 1992
dilacerata Hick. & A.Camus 1928 (A. Camus : n 16)
donnaiensis A.Camus 1935 (A. Camus : n 5)
geminata Hickel & A.Camus 1923, nom. illeg., non Small 1897
Cyclobalanopsis faadoouensis Hu 1951
Local names fa dou qing gang;
Range Vietnam (Annam, where it is abundant); Cambodia; China (SE Yunnan, W Guangxi); 1000-2000 m;
Growth habit 7-10 m usually, but may reach 25-28 m;
Leaves 7-14 x 2.5-4 cm; coriaceous; oblong-lanceolate; both sides glabrous; apex attenuate, acuminate to shortly caudate; base cuneate or oblique; margin thickened, not undulate, with small, obtuse teeth in apical 1/3; green, shiny, hairless above; hairless, nearly concolor beneath; midrib slightly raised adaxially, prominent below; 10-12 pairs of secondary veins at an angle of 40° from midrib; tertiary veins evident abaxially; petiole 1-2 cm, initially pubescent, then hairless; 
Fruits acorn 2.5-3.8 cm long, 1.8-2 cm wide, obovoid to ellipsoid; pale brown, densely silky, basal scar strongly convex 1 cm wide; enclosed 1/3 by cup; cup sessile, cup-shaped, less than 1.6 cm long and 2 cm wide, very thick (wall 3 mm), rusty tomentose, with 6-9 broad, distinctly toothed, pubescent rings; stylopodium persistent ; maturing first year in September; kernel edible; 

Bark, twigs and

bark rough, dotted; twig initially pubescent, becoming glabrous;  bud globose to broadly ovate;
Hardiness zone, habitat not hardy; prefers wet, peaty soils;
Miscellaneous -- A. Camus : n 7;
-- Sub-genus Cerris, Section Cyclobalanopsis;
-- Section Semiserrata, sub-section Semiserratae (Menitsky).
-- Threatened (IUCN Red List Category : CR)

-- In 2018, H.T. Binh & al. consider a "Q. langbianensis Complex"
in Vietnam and Cambodia, with 10 species : 7 species already described and often considered as synonyms of Q. langbianensis (Q. camusiae, Q. cambodiensis, Q. baniensis, Q. dilacerata, Q. blaoensis, Q. donnaiensis et Q. langbianensis) and 3 new species (Q. bidoupensis, Q. honbaensis, Q. baolamensis); actually, those 10 species share several features, morphologically speaking, which are :
- mature leaf 12-17 cm long, 3-5 cm wide, margin serrate from apical 1/3 to apical 5/6, acute to acuminate apex, cuneate or attenuate base, young leaves hairy but almost hairless once mature;

- acorn ovoid or globose or ellipsoid, 1/4 to 2/3 enclosed in the cup ; cup obconical or cup-shaped, with 5-9 concentric rings;
10 species slightly differ from each other, in having other minor features, or in lacking or not some of the shared features.

Subspecies and

Hickel & A. Camus 1923 (Camus n° 10) is a subspecies for Menitsky 1976
= Q.langbianensis subsp cambodiensis (Hick.
& A. Camus) Menitsky 1976
tree 7-10 m heigh ; leaves oval-oblong, 10-14 cm long, 3-5 cm wide; apex obtuse, base cuneate; margin entire weakly toothed near apex or often only crenate; 7-11 vein pairs, at an angle of 32-35° from midrib; petiole hairy becoming glabrous, 1.2-2 cm long; acorn subglobose, 3 cm long, 1.8-2 cm across, densely yellowish silky pubescent, with basal scare flat; cup sessile twice as wide as height, covering 1/5 to 1/4 of the nut, with 7-8 concentric, yellowish pubescent rings, the lower ones dentate; Cambodia (Bokor, Elephant Mount, 1000 m);
For today's Authors (Min Deng, Z.K. Zhou, A. Coombes, 2010) it is a synonym of Q. langbianensis. For Binh & Ngoc 2018, this taxon belong to the "Q. langbianensis Complex".