Description: Annual or short-lived perennial herbs or spindly shrubs, glabrous or hairy with glandular or non-glandular hairs.
Leaves alternate, radical and/or cauline, simple, margins entire to sinuate, petiolate or sessile.
Flowers solitary in leaf axils, or inflorescences panicle-like, rarely raceme-like with each flower subtended by a bract. Flowers bisexual, actinomorphic or slightly zygomorphic. Calyx tubular to narrow-campanulate, 5-lobed, persistent in fruit. Corolla tubular or trumpet-shaped; limb 5-lobed. Stamens 5, equal or unequal in length, often 4 reaching throat of corolla tube, the fifth shorter; anthers 2-locular, dorsifixed, dehiscing by longitudinal slits. Ovary 2-locular.
Fruit a capsule surrounded by persistent calyx, dehiscing by 4 or rarely 2 valves.
Distribution and occurrence: World: c. 60–70 species, mostly South America, also North America, SW Africa, southern Pacific & Australia. Australia: 17 species (16 species endemic, 1 species naturalized), all States.
Cleistogamous flowers which usually have very short corollas, often scarcely exceeding calyx, are found in some species. Many species are important drug plants. Commercial tobacco is mainly derived from N. tabacum L. and N. rustica L.
Text by B. J. Conn
Taxon concept:
| | Key to the species | |
| 1 | Perennial, spindly shrub 1–6 m high; corolla yellow | Nicotiana glauca |
| Annual or short-lived perennial herbs; corolla white or pink | 2 |
| 2 | Plant 1–3 m high; inflorescence short, dense, panicle-like; corolla white or pink | Nicotiana tabacum |
| Plant usually less than 1 m high; inflorescence loose, elongated, panicle- or raceme-like; corolla white
Back to 1 | 3 |
| 3 | Ellipsoid-headed glandular hairs present at least on inflorescence | 4 |
| Ellipsoid-headed glandular hairs absent
Back to 2 | 5 |
| 4 | Inflorescences many-branched when mature, leafless; corolla limb 6–13 mm diam., lobes obtuse to acute; seeds oblong to unequally 4 sided; leaves sparsely hairy, not glandular | Nicotiana forsteri |
| Inflorescences few-branched when mature, often leafy in lower part; corolla limb 10–25 mm diam., lobes notched; seeds reniform or acutely angled; leaves with sticky glandular hairs
Back to 3 | Nicotiana occidentalis |
| 5 | Stems and leaves pubescent all over | 6 |
| Stems and leaves glabrous, glabrescent, or pubescent near base only
Back to 3 | 8 |
| 6 | Corolla tube more than 25 mm long or, if shorter, the length more than 14 times the width (measured at top of calyx) | 7 |
| Corolla tube less than 25 mm long or, if longer, the length less than 14 times the width (measured at top of calyx)
Back to 5 | Nicotiana velutina |
| 7 | Corolla tube 20–40 mm long; upper 4 anthers not all at the same level | Nicotiana simulans |
| Corolla tube 35–45 mm long; upper 4 anthers all at the same level
Back to 6 | Nicotiana megalosiphon |
| 8 | Branches and leaves glabrous or basal leaves, stem bases and young shoots hairy; seeds reniform or C-shaped | 9 |
| Branches and leaves glabrescent; seeds C-shaped
Back to 5 | Nicotiana velutina |
| 9 | Corolla tube 17–55 mm long, distinctly broadening up to the limb; seeds reniform, rarely to 20 mm long | Nicotiana suaveolens |
| Corolla tube usually 8–18 mm long, rarely to 20 mm long, not distinctly broadening up to the limb; seeds C-shaped
Back to 8 | Nicotiana goodspeedii |
|
