Trifolium dubium |
Trifolium suffocatum |
|
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
small cluster clover, suffocated clover, suffocating clover |
|
Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs annual, 3–10 cm, glabrous or sparsely hairy. |
Stems | erect to prostrate, branched from base. |
procumbent or 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 ovate, 0.3–0.5 cm, margins entire, apex acuminate-subulate; petiole 1–6 cm; petiolules to 0.5 mm; leaflets 3, blades obovate or obcordate, 0.3–0.8 × 0.2–0.6 cm, base cuneate, veins prominent adaxially, margins finely toothed, apex truncate or retuse, surfaces glabrous or sparsely hairy. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
axillary, 10–20-flowered, dense, globose, 0.5–0.8 × 0.5–0.8 cm; involucres absent, stipules forming involucrelike structures, overtopping inflorescences. |
Peduncles | 1–1.5 cm. |
essentially absent. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
straight, 0.1 mm; bracteoles triangular, membranous, 0.5–1.2 mm, apiculate. |
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. |
3–5 mm; calyx tubular, 3–5 mm, slightly hairy or glabrous, veins 10, tube 2–3 mm, lobes subequal, lanceolate, curved in fruit, orifice open; corolla white, 2.5–3.5 mm, banner obovate, 2.5–3.5 × 1 mm, apex acute. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
ovoid-ellipsoid, 3–5 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
2, yellow, lenticular or reniform, 0.8–1 mm, minutely papillate. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium suffocatum |
|
Phenology | Flowering May–Oct. | Flowering Mar–Apr. |
Habitat | Disturbed ground, fields. | Roadsides, gravelly lawns. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–100 m. (0–300 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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CA; OR; WA; w Europe; n Africa [Introduced in North America; introduced also in s South America (Chile), w Asia, s Africa, Pacific Islands (New Zealand), Australia] |
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 suffocatum is known from Monterey and San Mateo counties in California, Benton and Coos counties in Oregon, and San Juan County in Washington. (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 | |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Linnaeus: Mant. Pl. 2: 276. (1771) |
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