Trifolium dubium |
Trifolium grayi |
|
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
andrews' clover, Gray's clover |
|
Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs annual, 10–40 cm, densely pubescent or glabrate. |
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 ovate, 0.5–1.5 cm, margins toothed or lacerate, apex acute-acuminate; petiole 1–15 cm; petiolules 1 mm; leaflets 3, blades elliptic, oblanceolate, or obovate, 2–2.5 × 1–1.5 cm, base cuneate, veins fine, margins dentate-serrate to crenulate, teeth shortly aristate, apex obtuse or broadly acute, surfaces pubescent or glabrate. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
axillary or terminal, 5–30-flowered, subglobose or globose, 1.8–3 × 2–3 cm; involucres bowl-shaped, 10–25 mm, lobes 6–16, sharply setaceous-toothed, sinuses shallow. |
Peduncles | 1–1.5 cm. |
2–15 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
straight, 0.5 mm; bracteoles absent. |
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. |
10–17 mm; calyx campanulate, 6–13 mm, pubescent, veins 5, tube 3–5 mm, lobes unequal, setaceous, abaxial inconspicuously 2- or 3-fid, adaxial unbranched, segments plumose, orifice open; corolla usually lavender or purple, sometimes purple with white tips, 8–16 mm, banner oblong, proximally inflated in fruit, distally narrowed into twisted tip, 3–5 × 10–13 mm, apex obtuse, truncate, or emarginate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
stipitate, ovoid-ellipsoid, 2.5–4 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1 or 2, pale brown, mottled, ellipsoid to mitten-shaped, 1.6–2 mm, rugose. |
2n | = 16, 28, 32. |
|
Trifolium dubium |
Trifolium grayi |
|
Phenology | Flowering May–Oct. | Flowering Apr–Jun. |
Habitat | Disturbed ground, fields. | Wet meadows, foothill slopes, pine woodlands. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–600 m. (0–2000 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 |
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 grayi, which ranges from San Luis Obispo County in the south to Mendocino County in the north, and eastward into Amador, Sacramento, and Tuolumne counties, has long been considered a variety of T. barbigerum and some authors claim that intermediates between the two species are encountered (J. S. Martin 1943; D. Isely 1998); others state that the two taxa are distinct (L. F. McDermott 1910; M. A Vincent and R. Morgan 1998). Trifolium andrewsii (A. Gray) A. Heller is an illegitimate superfluous name that pertains here. (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 | T. barbigerum var. andrewsii, T. barbigerum var. lilacinum, T. lilacinum |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Lojacono: Nuovo Giorn. Bot. Ital. 15: 189. (1883) |
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