Trifolium dubium |
Trifolium amphianthum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
peanut clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs perennial, 10–25 cm, glabrous or glabrate. |
Stems | erect to prostrate, branched from base. |
creeping, branched, rooting at nodes. |
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, 0.5–1 cm, margins entire, apex acute to acuminate; petiole 3–10 cm; petiolules 0.5–1 mm; leaflets 3, blades obcordate, 0.5–1.8 × 0.5–1.5 cm, base cuneate, veins thickened, margins entire or denticulate distally, apex usually deeply emarginate, rarely rounded, surfaces glabrous. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
axillary, 5–20-flowered, globose, 1–2.2 × 1–20 cm, chasmogamous erect, cleistogamous becoming subterranean; involucres formed of distinct, narrowly lanceolate bracts, 2.5–3.5 mm. |
Peduncles | 1–1.5 cm. |
chasmogamous 6–8 cm, cleistogamous ± sessile. |
Pedicels | reflexed, 0.2–0.5 mm; bracteoles a fringe of red setae. |
reflexed in fruit, cleistogamous pushing fruit underground, chasmogamous 1–8 mm, cleistogamous 4–20 mm; bracteoles lanceolate, 2–4 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. |
chasmogamous 8–11 mm, cleistogamous 4–5 mm; calyx campanulate, 3–5 mm, slightly pilose, veins 10, tube 1.5–2 mm, lobes subequal, adaxial pair connate proximally, sometimes nearly entire length, narrowly triangular-subulate, orifice open; corolla magenta or pink, 7.5–11 mm, banner broadly obovate-elliptic, 5–10 × 5–8 mm, apex rounded, emarginate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
stipitate, chasmogamous ellipsoid, cleistogamous ovoid-globose, chasmogamous longitudinally dehiscent, 3–6 mm, cleistogamous indehiscent, 3–6 mm. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
2–6 (chasmogamous), 1–3 (cleistogamous), tan, mitten-shaped, 1.2–1.5 mm, smooth. |
2n | = 16, 28, 32. |
= 16, 32. |
Trifolium dubium |
Trifolium amphianthum |
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Phenology | Flowering May–Oct. | Flowering Mar–Jun. |
Habitat | Disturbed ground, fields. | Sandy soils, prairies. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–200 m. (0–700 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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LA; TX |
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 amphianthum ranges in east-central Texas from Aransas County northward to Denton County, and eastward to San Augustine and Shelby counties; it is also recorded from Natchitoches and Rapides parishes in Louisiana. Trifolium amphianthum was collected once in Arkansas, but the specimen may have been from cultivation. The name Trifolium polymorphum Poiret applies to plants found in Argentina, Brazil, Paraguay, and Uruguay and has been misapplied to this North American endemic, as was done by M. Zohary and D. Heller (1984). Trifolium amphianthum is distinguished from T. polymorphum by its much larger leaves and flowers and essentially glabrous leaves and peduncles. (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. roemerianum |
Name authority | Sibthorp: Fl. Oxon., 231. (1794) | Torrey & A. Gray: Fl. N. Amer. 1: 316. (1838) |
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