Trifolium dubium |
Trifolium attenuatum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
Rocky Mountain clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs perennial, 5–30 cm, pubescent. |
Stems | erect to prostrate, branched from base. |
erect or ascending, cespitose, branched from base, numerous short stems. |
Leaves | pinnate; stipules ovate, 0.3–0.5 cm, margins entire, apex acute; petiole to 1.5 cm; lateral leaflet petiolules to 0.5 mm, terminal leaflet stalk 1–1.5 mm; leaflets 3, blades obovate to elliptic-lanceolate, 1–2 × 0.5–1.5 cm, base cuneate, lateral veins prominent, ± parallel, ascending, margins dentate distally, apex rounded or retuse, surfaces glabrous or sparsely hairy. |
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. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
axillary or terminal, 10–20+-flowered, globose, 2.3–3.5 × 2.5–4 cm; involucres formed of proximal bracteoles, bases sometimes connate. |
Peduncles | 1–1.5 cm. |
2–28 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
reflexed in fruit, 2–4 mm; bracteoles ovate, 2–4 mm, truncate or acuminate. |
Flowers | 2.8–3.5 mm; calyx campanulate, 1.5–2 mm, glabrous, veins 5, tube 0.8–1 mm, lobes unequal, longer than tube, adaxial 2 shorter, orifice open; corolla pale yellow becoming brown, 2.6–3.2 mm, not or slightly ribbed, banner persistent, spatulate, 2.6–3.2 × 2 mm, apex rounded to broadly acute. |
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 | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
oblong, 5–6 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1–3, brown, ovoid-reniform, 2.5 mm, smooth. |
2n | = 16, 28, 32. |
= 16, 48. |
Trifolium dubium |
Trifolium attenuatum |
|
Phenology | Flowering May–Oct. | Flowering Jun–Aug. |
Habitat | Disturbed ground, fields. | Subalpine and alpine slopes, open montane forests. |
Elevation | 0–2300 m. (0–7500 ft.) | 3000–3800 m. (9800–12500 ft.) |
Distribution |
AK; AL; AR; AZ; CA; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WY; BC; NB; NS; ON; PE; QC; SPM; c Europe; s Europe; w Asia [Introduced in North America; introduced also in s South America, e Asia (e China), n, s Africa, Pacific Islands (Hawaii, New Zealand), Australia]
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CO; NM
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Discussion | Trifolium dubium is often confused with Medicago lupulina Linnaeus; the latter may be distinguished by its toothed stipules, deciduous corollas, and shiny, black fruits. Little hop clover may be the co-called shamrock of Irish folklore (E. C. Nelson 1991; P. S. Wyse Jackson 2014); other candidates include other species of Trifolium or species of Medicago or Oxalis. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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. (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 11. | FNA vol. 11. |
Parent taxa | Fabaceae > subfam. Faboideae > Trifolium | Fabaceae > subfam. Faboideae > Trifolium |
Sibling taxa | ||
Synonyms | Chrysaspis dubia, T. minus | T. bracteolatum, T. petraeum, T. stenolobum |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Greene: Pittonia 4: 137. (1900) |
Web links |
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