New species, Hoya sungwookii (Apocynaceae, Asclepiadoideae), from southern Vietnam

A new species, Hoya sungwookii, discovered in southern Vietnam near Nha Trang Town (Khanh Hoa Province) is described and illustrated. It belongs to the type section of the genus and is distinguished from the morphologically closest H. ablongacutifolia (= H. graveolens) in glabrous pedicels, smaller flower 1.1–1.4 cm across, greenish ciliate calyx, corolla abaxially light green, small green to dark green corona 4.5–5 mm in diameter, 1.6–1.8 mm tall, small, 2–2.2 mm long, corona segments, and short corona segment inner angle, not exceeding anthers. Additionally, data on ecology, phenology, distribution of newly described species are presented, as well as its evaluated conservation status and color illustrations. Taking into consideration our new data, the genus in Vietnam currently includes 45 species.