Trifolium dubium |
Trifolium thompsonii |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
Thompson's clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs perennial, 35–50 cm, antrorse-strigose. |
Stems | erect to prostrate, branched from base. |
erect, 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 lanceolate, 3–4 cm, margins entire, apex acuminate; petiole 5–20 cm; petiolules to 1 mm; leaflets 5–7, blades linear, linear-elliptic, linear-lanceolate, often folded, falcate, 2–7 × 0.2–0.6 cm, base cuneate, veins thickened, margins setose, apex acute-setiform, surfaces pubescent. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
terminal, 60-flowered, in 10–12 whorls, globose or ovoid to subglobose, 3–5 × 3–4 cm; involucres absent. |
Peduncles | 1–1.5 cm. |
10–15 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
reflexed in fruit, 1–1.5 mm; bracteoles minute. |
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. |
20–23 mm; calyx campanulate, 6–8 mm, slightly pilose, veins 10–15, tube 2.5–3 mm, lobes equal, subulate, slightly pilose, orifice open; corolla rose-pink to purple, 18–22 mm, banner oblong, folded, 18–22 × 11–13 mm, apex rounded. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
flattened, lanceoloid-oblong, 6 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1 or 2, yellow, often mottled, mitten-shaped, 2.8–3 mm, smooth, glossy. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium thompsonii |
|
Phenology | Flowering May–Oct. | Flowering May–Jun. |
Habitat | Disturbed ground, fields. | Dry talus fans at base of slopes. |
Elevation | 0–2300 m. (0–7500 ft.) | 100–300 m. (300–1000 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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WA
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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 thompsonii is known from Chelan and Douglas counties (J. E. Canfield 1977). It is in the Center for Plant Conservation’s National Collection of Endangered Plants. (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 | Lupinaster thompsonii |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | C. V. Morton: J. Wash. Acad. Sci. 23: 270. (1933) |
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