Trifolium dubium |
Trifolium hybridum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
Alsike clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs perennial, 10–70 cm, glabrous or sparsely hairy. |
Stems | erect to prostrate, branched from base. |
erect or ascending, branched. |
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 obovate or lanceolate, 1–2.5 cm, margins entire or toothed, apex long-acuminate; petiole 1–21 cm; petiolules 1 mm; leaflets 3, blades usually obovate or ovate, rarely rhombic, 1–4 × 1–2.5 cm, base cuneate, veins prominent, margins sharply serrate, apex broadly acute, obtuse, or emarginate, surfaces glabrous. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
terminal or axillary, 10–70+-flowered, globose to subglobose, 1–2.5 × 1–2.5 cm, rachis not prolonged beyond flowers; involucres absent. |
Peduncles | 1–1.5 cm. |
2–10 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
strongly reflexed, 2–3.5 mm; bracteoles lanceolate, 1 mm. |
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. |
8–12 mm; calyx campanulate, 3.5–4 mm, glabrous or sparsely hairy, veins 10, tube 1.5–2 mm, lobes unequal, lanceolate-subulate, orifice open; corolla pale to dark pink, 7–10 mm, banner ovate-oblong, 6.5–10.5 × 4–6 mm, apex rounded-denticulate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
stipitate, ellipsoid, 3–7 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
2–4, tan, brown, or red-brown, mitten-shaped, 1–1.4 mm, smooth, dull. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium hybridum |
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Phenology | Flowering May–Oct. | Flowering May–Oct. |
Habitat | Disturbed ground, fields. | Roadsides, open woods, edges, fields, meadows, waste places. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–1800 m. (0–5900 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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AK; AL; AR; AZ; CA; CO; 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; SD; TN; UT; VA; VT; WA; WI; WV; WY; AB; BC; MB; NB; NL; NS; NT; ON; PE; QC; SK; YT; SPM; Greenland; Europe; w Asia [Introduced in North America; introduced also in South America, Europe, elsewhere in Asia, Africa, Pacific Islands, Australia]
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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 hybridum is widely cultivated as a forage crop. It may cause dermatitis in humans (J. W. Hardin and J. M. Arena 1974) and is implicated as a cause of dermatitis and biliary fibrosis in horses (C. Fisher 1995); the connection between the clover and the diseases is inconclusive (P. N. Nation 1989). (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 | Amoria hybrida, T. elegans |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Linnaeus: Sp. Pl. 2: 766. (1753) |
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