Trifolium dubium |
Trifolium lappaceum |
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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover |
burdock clover |
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Habit | Herbs annual, 20–40 cm, glabrous or sparsely hairy. | Herbs annual, 5–60 cm, hirsute or glabrous. |
Stems | erect to prostrate, branched from base. |
erect to decumbent, 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 oblong, 0.5–1.9 cm, margins entire, apex lanceolate-subulate; petiole 0.3–5 cm; petiolules 1 mm; leaflets 3, blades ovate to obovate, 0.5–1.5 × 0.3–2 cm, base cuneate, veins fine, margins denticulate to dentate, apex rounded, truncate, or emarginate, surfaces hirsute. |
Inflorescences | axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm; involucres absent. |
terminal, 40–60-flowered, globose or ovoid, burlike, not disarticulating at maturity, 1–1.4 × 1.8–2 cm; involucres absent. |
Peduncles | 1–1.5 cm. |
0.1–0.7 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. |
7–9 mm; calyx campanulate, 7–9 mm, glabrous, veins 20, tube 3 mm, lobes equal, longer than tube, setaceous becoming spinose, orifice hairy, open; corolla pinkish white, 6–10 mm, banner elliptic, 6–9 × 1.5–2 mm, apex emarginate. |
Legumes | stipitate, ellipsoid, 1.5–2 mm, short beaked. |
ovoid, leathery distally, transversely dehiscent, 1.5 mm, long-beaked. |
Seeds | 1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy. |
1, light brown, reddish, or yellow with reddish spots, ovoid, 1 mm, smooth, shiny. |
2n | = 16, 28, 32. |
= 16. |
Trifolium dubium |
Trifolium lappaceum |
|
Phenology | Flowering May–Oct. | Flowering Mar–Jun. |
Habitat | Disturbed ground, fields. | Fields, roadsides, grassy areas. |
Elevation | 0–2300 m. (0–7500 ft.) | 0–300 m. (0–1000 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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AL; FL; LA; MS; NC; NJ; PA; SC; TN; TX; s Europe; w Asia; n Africa; Atlantic Islands (Canary Islands) [Introduced in North America; introduced also in s South America (Uruguay), s Africa, Australia]
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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 lappaceum was introduced to the United States about 1903; it has been used as a winter annual pasture and hay crop (E. A. Hollowell 1939), as well as in roadside grass plantings as a nitrogen source. (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: Sp. Pl. 2: 768. (1753) |
Web links |
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