Tagetes

Annuals, perennials, subshrubs, or shrubs [perennials], mostly 10–80(–200) cm. Stems erect, branched distally or ± throughout. Leaves cauline; mostly opposite (distal sometimes alternate); petiolate or sessile; blades mostly lanceolate to oblanceolate overall, usually 1–3-pinnately lobed or -pinnatisect, ultimate margins toothed or entire, faces glabrous or hairy (oil-glands scattered and/or submarginal). Heads radiate or discoid, borne singly or in ± corymbiform arrays. Calyculi 0. Involucres narrowly cylindric or fusiform to turbinate or broadly campanulate, 1–12+ mm diam. Phyllaries persistent, 3–21+ in 1–2 series (connate to 7/8+ their lengths, usually streaked and/or dotted with oil-glands). Receptacles convex to conic, smooth or finely pitted, epaleate. Ray florets 0 or 1–8(–13+) (to 100+ in “double” cultivars), pistillate, fertile (except “double” cultivars); corollas yellow or orange, red-brown (with or without yellow/orange), or white. Disc florets 6–120+, bisexual, fertile; corollas greenish yellow to orange, sometimes tipped with red or red-brown, tubes much longer than or about equaling funnelform throats, lobes 5, deltate to lance-linear (equal or 2 sinuses deeper than others). Cypselae narrowly obpyramidal or fusiform-terete, sometimes weakly flattened, glabrous or hairy; pappi persistent, of 2–5(–10) dissimilar, distinct or connate scales in ± 1 series: 0–5+ oblong to lanceolate, erose-truncate or laciniate plus 0–2(–5) longer, subulate to aristate. x = 12.

Distribution

Tropical and warm-temperate America, especially Mexico, introduced in Old World.

Discussion

Species 40+ (4 in the flora).

Some Tagetes species (e.g., T. erecta) produce nematicidal thiophenes in their roots and have been shown to be effective controls for nematodes in diverse crops (cf., http://www.ncagr.com/agronomi/nnote1.htm).

Reports of “Tagetes minima L.” for Pennsylvania (cf. http://plants.usda.gov) are evidently rooted in an error for T. minuta. Report of T. pusilla Kunth (= T. filifolia Lagasca) for Maryland (http://plants.usda.gov) was not verified for this treatment.

Selected References

Neher, R. T. 1966. Monograph of the Genus Tagetes (Compositae). Ph.D. thesis. Indiana University.

Rydberg, P. A. 1915. Tagetes. In: N. L. Britton et al., eds. 1905+. North American Flora.... 47+ vols. New York. Vol. 34, pp. 148–159.

Soule, J. A. 1993. Systematics of Tagetes (Asteraceae–Tageteae) (Mexico, Argentina). Ph.D. thesis. University of Texas.

Lower Taxa

Tagetes erecta, Tagetes lemmonii, Tagetes micrantha, Tagetes minuta

Key

1	Leaf lobes (or simple blades) linear to filiform, 10–25(–35+) × 0.5–1.5 mm	Tagetes micrantha
1	Leaf lobes lance-elliptic or lanceolate to lance-linear, 12–25(–50+) × (2–)4–8(–12+) mm	> 2
2	Perennials, subshrubs, or shrubs	Tagetes lemmonii
2	Annuals	> 3
3	Heads in ± corymbiform clusters; peduncles 1–5+ mm; involucres 7–10+ × 1.5–3 mm	Tagetes minuta
3	Heads borne ± singly; peduncles 30–100(–150+) mm; involucres 10–22 × (3–)5–12+ mm	Tagetes erecta