Borrichia

Perennials, subshrubs, or shrubs, to 150 cm (rhizomatous, forming clonal colonies, roots fibrous, sometimes adventitious). Stems decumbent to erect, branched ± throughout (sap sticky-resinous). Leaves cauline; opposite; ± petiolate or sessile; blades (usually 1-nerved, sometimes obscurely 3- or 5-nerved) elliptic, linear, oblanceolate, obovate, or ovate (usually coriaceous or succulent), bases ± cuneate, margins entire or toothed (teeth often spine-tipped), faces glabrous or puberulent to villous and/or sericeous. Heads radiate, borne singly or (3–10) in cymiform arrays. Involucres globose or ovoid to hemispheric or broader, (5–)8–13(–18+) mm diam. Phyllaries persistent, 10–45 in 2–3 series (outer larger, elliptic to oblanceolate or ovate, apices acute, cuspidate, obtuse, rounded, or spine-tipped). Receptacles convex, paleate (paleae lanceolate to ovate, ± conduplicate, partially enclosing cypselae, apices often ± pungent). Ray florets 7–30, pistillate, fertile; corollas yellow. Disc florets 20–75, bisexual, fertile; corollas yellow, tubes shorter than funnelform throats, lobes 5, lance-triangular (anthers black with orange glands on connectives). Cypselae (gray to black) ± obcompressed, or obpyramidal and 3- or 4-angled (faces faintly finely reticulate); pappi persistent or tardily falling, (stramineous) coroniform or cupular (3–4-angled). x = 14.

Distribution

United States, Mexico, West Indies.

Discussion

Species 3 (3 species, including 1 hybrid, in the flora).

Leaves of Borrichia species are usually heteroblastic: leaves on primary stems are usually ± petiolate (sometimes with spine-tipped teeth on margins of petioles or near bases of blades) and larger and relatively broader than the usually sessile leaves on secondary stems.

Selected References

Semple, J. C. and K. S. Semple. 1977. Borrichia ×cubana (B. frutescens × arborescens): Interspecific hybridization in the Florida Keys. Syst. Bot. 2: 292–301.

Semple, J. C. 1978. A revision of the genus Borrichia Adans. (Compositae). Ann. Missouri Bot. Gard. 65: 681–693.

Lower Taxa

Borrichia arborescens, Borrichia frutescens, Borrichia ×cubana

Key

1	Leaves (at least mid cauline): margins entire or dentate to serrate (teeth remote, mostly toward apices), faces glabrous or sericeous; phyllaries (chartaceous in fruiting heads): apices acute, rounded, or obtuse; paleae: apices obtuse to acute	Borrichia arborescens
1	Leaves (at least mid cauline): margins usually dentate to serrate, rarely entire, faces usually villous (longer hairs) and/or sericeous (shorter hairs) to glabrate, rarely glabrous; phyllaries: apices cuspidate or spine-tipped; paleae: apices cuspidate or spine-tipped	> 2
2	Mid-cauline leaves (petioles or blade bases with spine-tipped teeth): margins dentate to serrate (usually only proximal 1/3–1/2, rarely most, of each margin); phyllaries (often reflexed, swollen in fruit): apices spine-tipped; paleae: apices spine-tipped	Borrichia frutescens
2	Mid-cauline leaves: margins dentate or serrate (at least mid portions, often undulate as well); phyllaries: apices cuspidate; paleae: apices cuspidate	Borrichia ×cubana