Oaks of the World

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  Quercus ngochoaensis
Author Binh & Son 2021
Synonyms
Local names
Range Vietnam (Mt Ngoc Hoa, in the Ba Vi National Park); 1100 m;
Growth habit 5 meters tall, girth 15 cm;
Leaves 4.5-7.5 cm X 2.1-3.2; thinly leathery; ovate or elliptic-ovate; apex acuminate; base broadly cuneate; margin serrate in apical 2/3, with 5-7 teeth both sides; both faces hairless; 7-10 veins pairs, at an angle of 45-60° with midrib, slightly raised adaxially, strongly prominent beneath as is the midrib; tertiary veins scalariform, remotely visible abaxially; petiole 1-1.5 cm long, white tomentose at first, glabrescent;
Flowers female inflorescenses axillary, erect;
Fruits acorn subglobose, 0.9-1.2 cm long, 0.8-1.2 wide, white tomentose, apex depressed and concave; solitary; sessile; stylopodium 1-1.2 mm long; basal scar 7-9 mm in diameter, slightly convex; cupule cup-shaped 1.2-1.4 cm wide, 0.8-1.1 cm high, enclosing 1/2 to 2/3 of nut; cupscales in 7-8 concentric rings, covered with whitish hairs, with margin entire except the 3 lower ones which are distinctly dentate; maturation in November;

Bark, twigs and
buds

bark whitish grey; twigs hairless, dark green, with lenticels; bud oblong to ellipsoid, 1-3 mm long, 0.5-1 mm wide; bud-scales imbricate into 4-6 rows, ovate-triangular, with obtuse apex and ciliate margin, covered both sides with whitish or yellowish-brown hairs;
Hardiness zone, habitat mixed forests of broadleaves and conifers; calcareous rocky soils;
Miscellaneous -- Sub-genus Cerris, Section Cyclobalanopsis;
-- Closely related to Q. glauca Thunb. from which it differs in having smaller leaves, shorter petioles, foliar margin distinctly serrate in apical 2/3, a cup-shaped cup enclosing to 2/3 of acorn, cup-scales in 7-8 concentric rings, a globose acorn;

-- Critically endangered, as there are only 20 mature trees in its range.

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