Trifolium dubium |
Trifolium reflexum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
buffalo clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs annual or biennial, 10–60 cm, villous or glabrate. |
Stems | erect to prostrate, branched from base. |
erect or ascending, unbranched or 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 broadly ovate, 1–2.5 cm, margins entire or denticulate, apex acute or acuminate; petiole 1–10 cm (distalmost 0.3–3.5 cm); petiolules 0.5–1.5 mm; leaflets 3, blades ovate, obovate, oblong, or rhombic, 1–4.5 × 0.7–2 cm, base cuneate, veins fine, margins dentate to denticulate, apex broadly acute, rounded, or emarginate, surfaces pubescent or glabrous. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
terminal or axillary, 10–50-flowered, globose to subglobose, 1.5–4 × 2–4 cm; bracteoles forming shallow, membranous cups, to 0.5 mm. |
Peduncles | 1–1.5 cm. |
2–8 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
reflexed in fruit, 5–12 mm; bracteoles broad-obovate, membranous, 0.5–1 mm, truncate to 2-fid. |
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. |
10–15 mm; calyx campanulate, 6–9 mm, pilose or glabrous, veins 10, tube 1–1.5 mm, lobes equal, narrowly triangular to subulate, 3–7 mm, margins green, sinuses broad, orifice open; corolla usually pink, magenta, or creamy white, sometimes bicolored, 9–14 mm, banner obovate-oblong, 9–14 × 5–8 mm, apex rounded or retuse, often erose-denticulate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
oblong, 4–5 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1–6, yellow to brown, purple-mottled, globose, 1.2–1.5 mm, slightly rugose. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium reflexum |
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Phenology | Flowering May–Oct. | Flowering Apr–Jun. |
Habitat | Disturbed ground, fields. | Clearings in forests, open woods, meadows, especially after fires. |
Elevation | 0–2300 m. (0–7500 ft.) | 200–500 m. (700–1600 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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AL; AR; DC; FL; GA; IA; IL; IN; KS; KY; LA; MD; MO; MS; NC; NE; NJ; OH; OK; PA; SC; TN; TX; VA; WV; ON
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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.) |
Nearly glabrous plants of Trifolium reflexum have been called var. glabrum Lojacono; var. reflexum is described as densely pubescent. The distinctions between these two varieties is inconsistent and may be based in part on age (M. A. Vincent 1991). (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 reflexa, T. adscendens, T. comosum, T. platycephalum |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Linnaeus: Sp. Pl. 2: 766. (1753) |
Web links |
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