Trifolium dubium |
Trifolium gracilentum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
pin point clover, slender clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs annual, 2–60 cm, glabrous. |
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 ovate-lanceolate, 0.5–2.5 cm, membranous, margins entire or slightly serrate, apex long-acuminate; petiole 0.5–9 cm; petiolules to 0.5 mm; leaflets 3, blades obovate to obcordate, 0.5–2.5 × 0.2–1.5 cm, base cuneate, veins moderately thickened, margins setose-serrulate, apex rounded, shallowly retuse, surfaces glabrous. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
axillary or terminal, 10–25-flowered, globose to subglobose, 0.5–2 × 0.5–2 cm, rachis prolonged beyond flowers; involucres a narrow, membranous, dentate rim, to 0.5 mm. |
Peduncles | 1–1.5 cm. |
1–9 cm. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
becoming dramatically reflexed, 3–4 mm; bracteoles low, cuplike, membranous, to 0.5 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. |
5–7.5 mm; calyx narrowly campanulate, 4.5–6.5 mm, glabrous, veins 10, tube 2–2.5 mm, lobes unequal, long-triangular, margins green or purple, orifice open; corolla white, pink, or purple, 5–8 mm, banner ovate, 5–8 × 3–4 mm, apex broadly rounded, retuse or apiculate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
ovoid-ellipsoid, 4–6 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1 or 2, tan to brown, mitten-shaped, 1.1–1.5 mm, smooth. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium gracilentum |
|
Phenology | Flowering May–Oct. | Flowering Mar–Jun. |
Habitat | Disturbed ground, fields. | Open, grassy areas, gravelly ridges, roadsides, adobe slopes, moist places. |
Elevation | 0–2300 m. (0–7500 ft.) | 50–1200 m. (200–3900 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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AZ; CA; NV; OR; WA; Mexico (Baja California)
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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.) |
Abundance of Trifolium gracilentum increases in response to burns (J. M. DiTomaso et al. 1999). The record of Trifolium gracilentum from South Carolina is a waif. (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. denudatum, T. exile, T. gracilentum var. exile, T. gracilentum var. inconspicuum, T. gracilentum var. reductum, T. inconspicuum |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Torrey & A. Gray: Fl. N. Amer. 1: 316. (1838) |
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