Scientific name: Hoya tamdaoensis Rodda & T.B.Tran
English name:
Vietnamese name: Cẩm cù tam đảo
Other name:

Lithophytic climber with white exudate in all vegetative parts, glabrous, except young stems sparsely pubescent with retrorse hairs. Stems slender, internodes (5—)8—12(—15) cm x 1.5-3 mm, dark green to brownish purple; adventitious root sparsely produced along the stem. Leaves wine-red when young; petiole recurved, held at an almost right angle to the lamina, 0.8-2 cm x 1.5—2.5 mm, dark green to brownish purple; lamina oblong-lanceolate, (4-)5-10 x (1.5—)2—3 cm, base attenuate-rounded, apex caudate, margin entire, reflexed in older leaves; venation pinnate, secondary veins in 4-7 pairs, borne at 70o-90o to midrib, anastomosing, tertiary venation reticulate, dark green above, glossy with occasional grey spots, midrib depressed above, raised underneath, lighter green with a slightly darker midrib and edge underneath; colleters one at each lamina base, triangular, 0.8-1 X 0.8-1 mm. Inflorescence pseudo-umbellate, convex; peduncle 3-10 cm X 1.8-2.5 mm diam., dark green to purplish brown, glabrous. Flowers (4-)10-15 per inflorescence; pedicel 2-2.5 cm X 0.8-1.2 mm diam., light green, glabrous. Calyx lobes broadly triangular, 1.5-2 X 1-1.5 mm wide, light green with purple spots, glabrous; basal colleter one per calyx lobe sinus, ovate to triangular, 1.5-2 X 1-1.2 mm, apex rounded. Corolla rotate, flat, 1.8-2.2 cm diam., tube 5-6 mm long, thickly pubescent inside, glabrous outside, lobes broadly triangular, 6-8 X 5.5-7 mm, white, margin recurved, apex acute, revolute, thickly pubescent inside with glabrous apex, glabrous outside. Corona staminal, 9-10 mm diam., 4-5 mm high, lobes ovate, 3.5-4.5 X 2.3-2.6 mm, concave above, underneath sulcate with inrolled margins, outer process apex rounded, inner process acuminate. Anthers ovate, ca. 1.3 X 1.2 mm, with apical round membranaceous appendage exceeding the style-head by 0.5-0.7 mm. Pollinia clavate, 650-750 X 270-320 ^m, narrowing towards the base, apex truncate, sterile edge all along the outer edge of the pollinium; corpusculum rhomboid, 300-400 X 180-220 ^m, apex acute; caudicle broad, spathulate, hyaline, ca. 150 X 100 ^m at the widest. Style-head 5-angled in cross section, with 5 lobes alternating with the stamens, style-head apex round, ca. 1 mm long, 2-2.5 mm broad at the base. Ovaries 2, ovate, 1.5-2 mm X ca. 1 mm wide at the base, light green, apex narrow. Fruit and seed not seen.

The new species is named after the collection locality, Tam Đảo National Park, Vietnam.

Distribution and ecology:

Only known from the type locality in Tam Đảo National Park, Vietnam. Hoya tamdaoensis was found growing epilithically on limestone covered by moss in evergreen lower montane forest