Sp. Pl. 1: 177. 1753.
Herbs, annual, biennial, or perennial; stolons absent. Stems erect, glabrous, glabrate, puberulent, hirsute, tomentose, or floccose, sometimes glabrescent, stipitate-glandular or eglandular. Leaves basal and cauline, alternate; stipules absent; petiole present or absent; blade not fleshy, leathery or not, margins entire, serrate, crenate, dentate, sinuate, or lobed. Inflorescences terminal, spikes, racemes, or panicles, flowers solitary or clustered in fascicles; bracts present. Pedicels present; bracteoles present or absent. Flowers bisexual; sepals 5, calyx radially or bilaterally symmetric, campanulate, lobes linear-oblong to elliptic or triangular; petals 5, corolla yellow to orange, white, purple, cream, or pink, sometimes with purple center or red-tinged tips, radially or bilaterally symmetric, rotate with petals spreading to deflexed or shallowly cupulate, abaxial lobes 3, adaxial 2; stamens 5, adnate to base of corolla, equal to subequal or anterior pair longer, filaments densely villous, sometimes anterior pair glabrous, staminode 0; ovary 2-locular, placentation axile; stigma capitate or spatulate. Fruits capsules, ovoid to ellipsoid-ovoid, broadly ellipsoid, ovoid-globular, or subglobular, dehiscence septicidal. Seeds 50–300, tan or brown to orangish, conic to cylindric, usually pitted and rugose, appearing transversely and longitudinally ribbed, wings absent. x = 6.
Introduced; Europe, Asia, ne Africa, introduced also in Mexico, South America, elsewhere in Africa (Tunisia), Pacific Islands, Australia.
Species 300–360 (12 in the flora).
Chromosome counts of 2n = 18, 26, 30, 32, 34, 36, 40, 44, 45, 48, 50, 64, and 66 have been reported for species of Verbascum. A base number is not clear, but x = 6 appears to be a reasonable fit (2n = 18, 30, 36, 48, and 66 would thus be polyploid levels). In any case, the range of numbers reflects both polyploidy and dysploidy.
Stamen number, placenta structure (entire and sessile versus two-fid and stalked), capsule shape, and number of flowers per node/bract have been used as diagnostic characters to distinguish Celsia Linnaeus and Staurophragma Fischer & C. A. Meyer as segregates from Verbascum (S. Murbeck 1925; A. Huber-Morath 1973; F. A. Karaveliogullari and Z. Aytac 2008). Huber-Morath (1978) included Celsia and Staurophragma within Verbascum. All species treated here are Verbascum in the strict sense.
Taxonomic treatments of Verbascum have been inconsistent in use of rank for infraspecific taxa; both varieties and subspecies appear in this treatment as well. Since all of our taxa are introduced to North America, further study of the species in their native environs is warranted before any uniformity can be established. In any case, use of one rank or the other does not imply a biological or evolutionary difference.
Hybrids are commonly produced among many combinations of parents. Verbascum thapsus, which is the most common and widespread of the species in the flora area, is known to have formed four hybrids in North America; see species discussions for nothospecies and purported parental species. Verbascum ×ramigerum Link ex Schrader [V. densiflorum × V. lychnitis] has been reported in Europe; it and other combinations may be expected in the flora area.
Plants of Verbascum collected as weeds in a lawn in Duluth, Minnesota, in 2001 and 2002 (Schimpf DJS318, DJS327, MIN), have been identified as V. chaixii Villars (http://plants.usda.gov); they perhaps are hybrids with V. nigrum as one of the parents (Dirk Albach, pers. comm.). The leaves are glabrate, the basal ones ovate-elliptic, subentire to shallowly crenate, and subpetiolate, and the cauline ones mostly non-clasping; the inflorescences are stipitate-glandular, unbranched, with flowers in loosely overlapping clusters of three to six; corollas are white to yellowish with pellucid glands; and staminal filaments all are villous with violet hairs. Without an unequivocal identification and evidence that they have become naturalized, they are not formally treated here.
|1||Flowers solitary in axils at least distally.||> 2|
|2||Corollas purple to violet; bracteoles 0; cauline leaves abruptly smaller distally.||Verbascum phoeniceum|
|2||Corollas yellow, sometimes white or pink (V. blattaria); bracteoles 0 or 2; cauline leaves gradually smaller distally.||> 3|
|3||Pedicels 5–11(–15) mm; bracteoles 0; stems and leaves glabrous or glabrate.||Verbascum blattaria|
|3||Pedicels (0–)1–3 mm; bracteoles 2; stems and leaves densely stipitate-glandular, sometimes also sparsely hiruste-villous.||Verbascum virgatum|
|1||Flowers mostly in clusters of 2–10.||> 4|
|4||Inflorescences unbranched, sometimes branched from proximal nodes.||> 5|
|5||Basal and proximal cauline leaf blades: bases shallowly cordate to nearly truncate, surfaces sparsely tomentose to glabrate, abaxial soon glabrescent, sometimes both glabrate; filaments villous, hairs purple to violet.||Verbascum nigrum|
|5||Basal and proximal cauline leaf blades: bases attenuate, surfaces densely and persistently tomentose; filaments villous or glabrous, hairs yellowish to whitish.||> 6|
|6||Flower clusters loosely overlapping.||Verbascum bombyciferum|
|6||Flower clusters densely overlapping or remote proximally.||> 7|
|7||Cauline leaves: bases not decurrent, rarely slightly so.||Verbascum phlomoides|
|7||Cauline leaves: bases decurrent.||> 8|
|8||Corollas 14–20(–30) mm diam., pellucid glands relatively numerous; anthers yellow; stigmas capitate; pedicels mostly or completely adnate to rachis.||Verbascum thapsus|
|8||Corollas 30–55 mm diam., pellucid glands absent or relatively few; anthers orange; stigmas spatulate; pedicels free or adnate to rachis at base.||Verbascum densiflorum|
|4||Inflorescences freely branched, sometimes unbranched (V. densiflorum, V. nigrum) or branched from proximal nodes and forming panicles (V. nigrum).||> 9|
|9||Leaf surfaces persistently tomentose.||> 10|
|10||Filaments: proximals glabrous, distal pairs villous; cauline leaves: bases long-decurrent.||Verbascum densiflorum|
|10||Filaments villous; cauline leaves: bases not decurrent or short-decurrent.||> 11|
|11||Leaf blade margins sinuate to incised or incised-lobed; flowers remote, clustered, rarely solitary; pedicels 2–5 mm; filament hairs violet to purple.||Verbascum sinuatum|
|11||Leaf blade margins entire or minutely serrate-dentate; flowers loosely overlapping, clustered; pedicels (3–)5–12 mm; filament hairs whitish to yellowish.||Verbascum speciosum|
|9||Leaf surfaces glabrate, sometimes abaxial surfaces sparsely persistently hairy and soon glabrescent.||> 12|
|12||Basal and proximal cauline leaves shallowly cordate or nearly truncate to a narrow petiole 5–15(–20) mm; filament hairs purple to violet; inflorescences unbranched, sometimes branched from proximal nodes, narrowly conic panicles.||Verbascum nigrum|
|12||Basal leaves sessile or basally attenuate and sessile, less commonly with petiolar regions 10–50 mm, cauline leaves sessile; filament hairs yellow to whitish; inflorescences freely branched, loosely conic to broadly cylindric panicles, sometimes unbranched.||> 13|
|13||Cauline leaves: bases not clasping or slightly so, surfaces thinly tawny- to gray-tomentose, abaxial soon glabrescent, adaxial persistent, closely adherent; bracts linear to narrowly lanceolate, 8–15 mm; pedicels 6–11 mm; corollas white, sometimes yellowish.||Verbascum lychnitis|
|13||Cauline leaves: bases distinctly clasping or subclasping, surfaces densely and loosely white-floccose, glabrescent, especially abaxially, sometimes thin-persistent adaxially; bracts linear, 3–5 mm; pedicels (1–)2–5(–7) mm; corollas yellow.||Verbascum pulverulentum|