Trifolium attenuatum
Pittonia 4: 137. 1900.
Herbs perennial, 5–30 cm, pubescent. Stems erect or ascending, cespitose, branched from base, numerous short stems. Leaves palmate; stipules lanceolate, 1.8–2 cm, margins entire, apex acute-acuminate; petiole 2.5–10 cm; petiolules to 0.5 mm; leaflets 3, blades linear, lanceolate, or narrowly elliptic, 1.5–6 × 0.3–1 cm, base cuneate, veins moderately thickened, margins entire, apex acuminate or narrowly acute, surfaces glabrous or pubescent. Peduncles 2–28 cm. Inflorescences axillary or terminal, 10–20+-flowered, globose, 2.3–3.5 × 2.5–4 cm; involucres formed of proximal bracteoles, bases sometimes connate. Pedicels reflexed in fruit, 2–4 mm; bracteoles ovate, 2–4 mm, truncate or acuminate. Flowers 15–22 mm; calyx campanulate, 8–15 mm, pubescent, veins 10, tube 2.5–7 mm, lobes unequal, subulate, orifice open; corolla red-purple, 16–20 mm, banner broadly oblong-elliptic, 16–20 × 6–7 mm, apex acute, apiculate. Legumes oblong, 5–6 mm. Seeds 1–3, brown, ovoid-reniform, 2.5 mm, smooth. 2n = 16, 48.
Phenology: Flowering Jun–Aug.
Habitat: Subalpine and alpine slopes, open montane forests.
Elevation: 3000–3800 m.
Discussion
Trifolium attenuatum ranges from Park County in Colorado southward through southern and southwestern Colorado to northern and central New Mexico.
J. M. Gillett (1965) found both diploid and hexaploid populations of Trifolium attenuatum but was unable to find morphological distinctions between diploid and hexaploid individuals. Using flavonoid chemotaxonomy, E. V. Parups et al. (1966) found close associations between T. attenuatum, T. brandegeei, and T. haydenii.
Trifolium lilacinum Rydberg (1901), which pertains here, is a later homonym of T. lilacinum Greene (1896) and thus illegitimate.
Selected References
None.