Herbs, shrubs, or small trees, with soft wood, annual, biennial, or short-lived perennial, often rosette-forming, from taproot or rarely horizontal rootstock (forming colonies), sparsely to densely viscid-pubescent with simple hairs, rarely glabrous. Stems usually erect, sometimes branching from base. Leaves alternate, densely clustered in rosette-forming species, sessile or petiolate; petiole often winged; blade simple, margins entire or irregularly and obscurely crenate and sometimes undulate. Inflorescences terminal or apparently axillary, cymose, usually forming false racemes, or glomerulate. Flowers bisexual, 5-merous (fasciated with increased parts only in cultivars), radially symmetric or somewhat bilaterally symmetric, especially in androecium; calyx tubular or narrowly campanulate, 5-lobed, lobes persistent, usually deltate or triangular, equal or unequal, usually slightly accrescent and mostly enclosing capsule; corolla white to cream, variously marked or tinged with pink or purple, or yellow-green, radial or more commonly at least somewhat bilateral, tubular, funnelform, or salverform, limb deeply 5-lobed to ± entire, lobes, if present, rounded to deltate, sometimes emarginate; stamens 5, inserted variously from near base of corolla tube to near apex, sometimes unequal (2 + 2 + 1), on equal filaments or filaments of unequal length with one inserted at a different level and usually shorter than the other 4; anthers dorsifixed (or appearing basifixed), ellipsoid to globose, dehiscing by longitudinal slits; ovary 2-carpellate (irregularly more in some cultivars); style filiform, straight or curved; stigma capitate or slightly 2-lobed. Fruits capsules, usually ovoid, sometimes narrowly so, 2–4-valved (occasionally many-valved in cultivars), dehiscent apically with long septicidal cleft and shorter loculicidal cleft. Seeds angular to oblong (minute), occasionally somewhat reniform. x = (9, 10), 12, (16, 18, 19), 24.

Distribution

North America, Mexico, West Indies, Central America, South America, s Africa, Australia, introduced widely.

Discussion

Species ca. 75 (12 in the flora).

Nicotiana is recognizable by its tubular flowers and usually sticky pubescence. Of the species occurring in North America, only N. glauca is not sticky-pubescent. The genus has long been of interest due the high number of allopolyploid species (T. H. Goodspeed 1954; M. W. Chase et al. 2003; E. W. McCarthy et al. 2015).

Most species of Nicotiana in the flora area have distinct basal rosettes until flowering occurs, and cauline leaves usually differ in morphology from those in the basal rosette. Many species occur as short-lived perennials in areas without frost, but occur as annuals where winters are harder. The tree tobacco (N. glauca) is the only truly woody species occurring in North America.

Species of Nicotiana that bloom in the evening usually have white or cream flowers and are pollinated by moths, while day-flowering species have yellow, pink, or cream flowers and are pollinated by bees; however, this overall pattern does not hold strictly true. Nicotiana attenuata has become a model system for the study of the complex interplay between pollinators and herbivores in the evolution of floral and other traits (for example, C. Diezel et al. 2011; D. Kessler et al. 2015).

Nicotiana species are often cultivated and occur occasionally as garden or greenhouse escapes. Nicotiana alata Link & Otto and N. × sanderae W. Watson have been reported for the flora area but are known only as ephemerals or from cultivation. Some records of N. alata are possible misidentifications for N. longiflora, from which N. alata differs in its strongly decurrent cauline leaves and larger corollas with wider tubes. Nicotiana × sanderae has striking red salverform corollas; various horticultural hybrids of this long-flowered species are possible ephemeral occurrences on waste heaps.

The two tobaccos of commerce, Nicotiana rustica and N. tabacum, are cultivated as orna­mentals or as sources of leaves for human use. Although most herbarium specimens from the flora area are clearly from cultivation, both taxa are sometimes adventive.

The small seeds and weedy habits of Nicotiana species predispose them to become invasive; for example, the non-native species N. glauca is a common component of ecosystems in western North America. This propensity to grow in disturbed areas means cultivated species are likely to become established briefly in areas where soil is loose or in old garden sites.

Selected References

None.

Lower Taxa

Nicotiana acuminata, Nicotiana attenuata, Nicotiana clevelandii, Nicotiana glauca, Nicotiana longiflora, Nicotiana obtusifolia, Nicotiana plumbaginifolia, Nicotiana quadrivalvis, Nicotiana repanda, Nicotiana rustica, Nicotiana sylvestris, Nicotiana tabacum

Key

1	Tubular portion of corollas (tube + throat) greenish yellow, pale yellow, or bright yellow, often with green limb; cauline leaves petiolate.	> 2
2	Leaf blades glaucous, glabrous; corolla tubes bright yellow to greenish yellow, limb usually a distinct color from tube, often bright green; small trees or shrubs.	Nicotiana glauca
2	Leaf blades not glaucous, viscid-pubescent; corolla tubes pale yellow to greenish yellow, limb same color as tube; short-lived perennials or annual herbs.	Nicotiana rustica
1	Tubular portion of corollas (tube + throat) ivory, cream, white (often tinged green, gray, or purple), pink, or occasionally red (N. tabacum); cauline leaves petiolate, sessile, or variously clasping.	> 3
3	At least some cauline leaves with a distinct petiole (very short in N. clevelandii and N. quadrivalvis).	> 4
4	Tubular portion of corollas greater than 2 times calyx length (including lobes); inflorescences usually branched, somewhat (not densely) leafy.	> 5
5	Corolla limbs circular, lobes deltate or emarginate; styles longer than longest stamens; calyces with dark midveins, trichomes without enlarged bases.	Nicotiana acuminata
5	Corolla limbs pentagonal (occasionally circular), lobes broadly triangular; styles shorter than longest stamens; calyces uniformly green, trichomes with enlarged bases.	Nicotiana attenuata
4	Tubular portion of corollas less than or equaling 2 times calyx length (including lobes), if greater than 2 times calyx length then limb greater than 2 cm diam.; inflorescences usually unbranched, densely leafy to bracteate.	> 6
6	Stamens included in throat: corolla limbs to 1 cm diam.; calyx lobes unequal, one longer than tubular portion of calyx.	Nicotiana clevelandii
6	Stamens exserted from throat; corolla limbs 2+ cm diam.; calyx lobes ± equal.	Nicotiana quadrivalvis
3	Cauline leaves sessile or with variously clasping bases (proximalmost near rosette sometimes appearing petiolate).	> 7
7	Corolla tubes pale greenish cream to pink or red, throat 0.5 cm diam., tubular portion straight or strongly curved and dilated distally.	Nicotiana tabacum
7	Corolla tubes white or cream (occasionally appearing pale yellow in very old flowers), often tinged with green, gray, or purple, throat 0.1–0.6 cm diam., tubular portion straight, variously shaped.	> 8
8	Corollas usually 5 cm or shorter.	> 9
9	Corolla length (excluding limb) to 2 times limb diam.; basal leaves not in distinct rosette.	Nicotiana obtusifolia
9	Corolla length (excluding limb) 2+ times limb diam.; basal leaves in distinct rosette.	> 10
10	Anthers to 0.1 mm (filaments free for at least some of their length); corollas glabrous or minutely puberulent (not cobwebby-pubescent) internally; distal cauline leaf blades lanceolate to linear-lanceolate.	Nicotiana plumbaginifolia
10	Anthers appearing sessile (filaments fused to corolla throughout their entire length); corollas cobwebby-pubescent internally; distal cauline leaf blades oblong-ovate or pandurate.	Nicotiana repanda
8	Corollas usually longer than 5 cm.	> 11
11	Tubular portion of corollas inflated and ventricose in middle to distal 1/3, slightly curved, corollas white; inflorescences panicles with congested branches, appearing moplike.	Nicotiana sylvestris
11	Tubular portion of corollas gradually widening distally, straight, corollas white or grayish white; inflorescences false racemes, occasionally few-branched.	> 12
12	Corolla throat constricted; filaments unequal, free for at least some of their length (anthers not sessile); cauline leaves sessile, blade lanceolate or linear, base auriculate.	Nicotiana longiflora
12	Corolla throat gaping; filaments equal, fused to corolla along their entire length (anthers appearing sessile); cauline leaves sessile, blade pandurate or oblong-ovate, base clasping.	Nicotiana repanda