Trifolium bifidum |
Trifolium dubium |
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notch-leaf clover, Pinole clover, piñole clover |
least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
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Habit | Herbs annual, 5–55 cm, sparsely pubescent or glabrous. | Herbs annual, 20–40 cm, glabrous or sparsely hairy. |
Stems | erect, branched. |
erect to prostrate, branched from base. |
Leaves | palmate; stipules ovate to lanceolate, 0.8–1.5 cm, margins entire or slightly serrate, apex acicular; petiole 1–7 cm; petiolules to 0.5 mm; leaflets 3, blades narrowly obcordate, obovate, oblanceolate, or linear, 1–2.5 × 0.3–0.7 cm, base cuneate, veins moderately thickened, margins serrate distally or entire, apex rounded, truncate, shallowly to deeply retuse, or deeply 2-fid, surfaces glabrous or hairy abaxially along midvein. |
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. |
Inflorescences | axillary or terminal, 5–30-flowered, globose to subglobose, 0.8–1.5 × 0.8–1.5 cm, rachis prolonged beyond flowers; involucres a very narrow rim, to 0.5 mm. |
axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
Peduncles | 3–8 cm. |
1–1.5 cm. |
Pedicels | reflexed in fruit, 1–3 mm; bracteoles broadly triangular, membranous, to 0.5 mm. |
reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
Flowers | 6–8 mm; calyx campanulate, 3–3.6 mm, slightly hairy or glabrous, veins 10, tube 1–1.5 mm, lobes unequal, subulate, margins green or purple, orifice open; corolla pink or purple, 5–7 mm, banner elliptic to oblong, 5–7 × 3–4 mm, apex rounded, apiculate. |
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. |
Legumes | stipitate, obovoid, 3–4 mm. |
stipitate, ellipsoid, 1.5–2 mm, short beaked. |
Seeds | 1 or 2, brown, mottled, oblong, 2–3 mm, smooth. |
1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
2n | = 16. |
= 16, 28, 32. |
Trifolium bifidum |
Trifolium dubium |
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Phenology | Flowering Apr–Jun. | Flowering May–Oct. |
Habitat | Open woodlands, fields, roadsides, slopes, stream margins, meadows. | Disturbed ground, fields. |
Elevation | 0–1200 m. (0–3900 ft.) | 0–2300 m. (0–7500 ft.) |
Distribution |
CA; OR; WA; BC; Mexico (Baja California)
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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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Discussion | Trifolium bifidum ranges from Baja California, Mexico, northward through California to scattered sites in Oregon, Washington, and British Columbia. Recent re-evaluation of Trifolium bifidum and related species showed complete overlap in characters for the two varieties that have been recognized previously, with no clear distinctions between them (L. Rogers, pers. comm.). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
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.) |
Source | FNA vol. 11. | FNA vol. 11. |
Parent taxa | Fabaceae > subfam. Faboideae > Trifolium | Fabaceae > subfam. Faboideae > Trifolium |
Sibling taxa | ||
Synonyms | T. bifidum var. decipiens, T. greenei, T. hallii | Chrysaspis dubia, T. minus |
Name authority | A. Gray: Proc. Calif. Acad. Sci. 3: 102. (1864) | Sibthorp: Fl. Oxon., 231. (1794) |
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