Trifolium sonorense
Phytoneuron 2018-1: 1, fig. 1. 2018.
Herbs perennial, 25–38+ cm, pubescent. Stems prostrate, branched. Leaves palmate; stipules narrowly triangular, 0.7–1.7 cm, margins entire or finely serrulate, apex usually acute or acuminate, sometimes 2-fid; petiole 0.3–5 cm; petiolules to 1 mm; leaflets 3, blades obovate to obcordate, 0.9–1.6 × 0.7–1.2 cm, base cuneate, veins moderately thickened, margins serrate to weakly so, apex rounded or emarginate, mucronulate, surfaces slightly hairy abaxially, glabrous adaxially. Peduncles 2.8–5 cm. Inflorescences axillary, 10–20-flowered, depressed-globose or globose, 0.8–1.6 × 0.9–1.6 cm, rachis prolonged beyond flowers; involucres a narrow rim, or slightly proximally connate bracteoles of proximal flowers, 0.1–0.5 mm. Pedicels reflexed in fruit, 1–3 mm; bracteoles linear-triangular, 0.5 mm. Flowers 5.7–6.7 mm; calyx tubular, 3.3–6.5 mm, pubescent, veins 10, tube 0.8–1 mm, lobes subequal, narrowly triangular, orifice open; corolla white or pink, 5.3–6.5 mm, banner obovate, 5.3–6.5 × 2.8–3.8 mm, apex broadly rounded or broadly acute. Legumes obovoid, 4.3–4.4 mm. Seeds 2, brownish orange or olive-brown, globose or broadly reniform, 1.2–1.7 mm, smooth. 2n = 16.
Phenology: Flowering Aug–Oct.
Habitat: Dry stream banks, grassy places.
Elevation: 1500–1800 m.
Distribution
Ariz., Mexico (Chihuahua, Jalisco, Sinaloa, Sonora).
Discussion
Trifolium sonorense has long been equated with T. amabile Kunth, from which T. K. Ahlquist (2012) and also Ahlquist & M. A. Vincent have shown it to be distinct by longer sepal lobes (more than 3 mm), keel petal claws (more than 1.7 mm), and filament tubes (more than 3.6 mm). Trifolium sonorense is known from western Mexico and southernmost Arizona (Cochise County), largely in the Sonoran Desert region, and in mountainous Jalisco.
Selected References
None.