Osmanthus, Loureiro, 1790

Diep, Tran Thi Ngoc, Doan, Ha Thi Thanh, Quang, Bui Hong, Averyanov, Leonid V., Lyskov, Dmitry F., Samigullin, Tahir H., Sennikov, Alexander N. & Nuraliev, Maxim S., 2025, An overview of the genus Osmanthus (Oleaceae) in Vietnam, with two new records and lectotypifications, Phytotaxa 684 (1), pp. 33-54 : 36

Key to the species of Osmanthus in Vietnam

1. Calyx 3–4 mm long; corolla tube longer than lobes, 6–9 mm long .................................................. O. suavis (sect. Siphosmanthus)

- Calyx 1–1.5 mm long; corolla tube shorter than lobes, 0.25–2.5 mm long .......................................................................................2

2. Leaf blade (4)7–11(15) × (1)2–4(5) cm; inflorescence many-flowered (with 9–18 flowers); style 0.5 mm long, stigma bilobed ..... ............................................................................................................................................................. O. fragrans (sect. Osmanthus )

- Leaf blade 3–19 × 1–6 cm; inflorescence several-flowered (with 5–8(12) flowers); style 1.5–2 mm long, stigma capitate and sometimes slightly bilobed .................................................................................................................................................................3

3. Petiole puberulous at least when young; leaf blade glabrous with midrib puberulous adaxially especially at base, ovate to elliptic or rarely obovate, 3–7 × 1–3 cm, margin entire or with up to 3(5) large strong spiny teeth per side, teeth 3–11 mm long ................ ..................................................................................................................................................... O. heterophyllus (sect. Osmanthus )

- Petiole glabrous or rarely hairy; leaf blade entirely glabrous, ovate-lanceolate, 5–19 × 2–6 cm, margin entire or spinose dentate with ca. 20–30 teeth per side, teeth 2–3 mm long.......................................................................... O. yunnanensis (sect. Ciliatorum)