Cytisus
Fl. Atlant. 2: 139. 1798. name conserved
Shrubs [subshrubs or trees], unarmed [armed]. Stems green, gray-green, or brownish green, usually ascending or erect, sometimes becoming pendent [prostrate], angled or terete [grooved], pubescent or glabrescent. Leaves alternate, odd-pinnate, sometimes reduced or absent in C. multiflorus; stipules present, caducous, lanceolate; petiolate; leaflets 1–5, stipels absent, blade margins entire, surfaces pubescent or glabrous. Inflorescences 1–7(or 8)-flowered, axillary and terminal, racemes or glomerules; bracts present, subpersistent or caducous, usually small, leaflike, 1–3-foliolate; bracteoles paired proximal to calyx. Flowers papilionaceous; calyx cylindric or campanulate, 8–9 mm, lobes 5, connate most of their length, shallowly lobed; corolla yellow or white [pink, purple], usually glabrous, banner reflexed or not; stamens 9 or 10, monadelphous [diadelphous]; anthers basifixed; ovary usually sessile, rarely stipitate; style abruptly incurved near middle or gently curved ± throughout, glabrous; stigma terminal. Fruits legumes, sessile or short-stipitate, laterally compressed or inflated, oblong or linear-oblong, base acuminate to acute, apex acute to rounded, explosively dehiscent, not constricted between seeds, pubescent or glabrous. Seeds 3–12, reniform, ovoid, or rounded, with callous appendage. x = 12.
Distribution
Introduced; s, w Europe, nw Africa, n Atlantic Islands, introduced also in s South America, Pacific Islands (New Zealand), Australia.
Discussion
Species ca. 50 (4 in the flora).
Chamaecytisus has been treated as distinct (for example, D. Isely 1998); molecular phylogenies have indicated that its species are embedded within the evolutionary structure of Cytisus (E. Käss and M. Wink 1995; P. Cubas et al. 2002).
Cytisus villosus Pourret, a native of southwestern Europe, has been reported as a waif in New York State (R. S. Mitchell and G. C. Tucker 1997). It also occurs in a small population in Victoria, British Columbia (Lomer 8672, UBC).
Selected References
None.
Key
| 1 | Twigs terete, grayish or brownish green, becoming pendent; leaflet blades 10–30 mm; inflorescences pendent, (1–)3–7(or 8)-flowered; calyces cylindric, 8–9 mm, abaxial lips 3-lobed; seeds black, ovoid or rounded. | Cytisus proliferus |
| 1 | Twigs 5–10-angled, green, erect or ascending; leaflet blades 2–7(–9) mm; inflorescences erect, 1(–3)-flowered; calyces campanulate, 5–7 mm, lips barely lobed; seeds olivaceous to dark brown, reniform. | > 2 |
| 2 | Twigs 8–10-angled; calyces appressed-pubescent; legumes inflated, densely white-hairy. | Cytisus striatus |
| 2 | Twigs 5-angled; calyces glabrous, puberulent, or villous; legumes laterally compressed, glabrous or margins villous. | > 3 |
| 3 | Calyces glabrous or puberulent; corollas usually yellow, rarely white (then unmarked), wings sometimes reddish; legumes narrowly oblong, 3.1–4(–5.5) cm. | Cytisus scoparius |
| 3 | Calyces villous; corollas white, banner with medial dark line; legumes linear- oblong, 2.5–3 cm. | Cytisus multiflorus |