Trifolium vesiculosum |
Trifolium subterraneum |
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arrow-leaf clover |
burrowing clover, subclover, subterranean clover, subterranean trefoil |
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Habit | Herbs annual, 15–70 cm, glabrous. | Herbs annual, 10–80 cm, glabrous or appressed-pubescent. |
Stems | erect or ascending, branched. |
prostrate to ascending, branched. |
Leaves | palmate; stipules linear-lanceolate, 1–3.5 cm, margins entire, apex subulate or setaceous; petiole 0.5–10 cm; petiolules 1 mm; leaflet 3, blades obovate to oblong, elliptic or lanceolate, 0.5–4 × 0.5–1.5 cm, base cuneate, veins prominent, thickened, margins spinulose-denticulate, apex apiculate, surfaces glabrous. |
palmate; stipules ovate, 0.5–3 cm, margins entire or slightly toothed, ciliate, apex acute to acuminate; petiole 1–20 cm; petiolules 1 mm; leaflets 3, blades broadly obcordate, 0.8–2.8 × 1–3 cm, base cuneate, veins delicate, widely spaced, margins mostly entire, slightly dentate distally, apex emarginate, surfaces appressed-sericeous. |
Inflorescences | terminal or axillary, 50–100+-flowered, globose, ovoid, or oblong, 3–6 × 2–3.5 cm; involucres absent. |
axillary, elongate and reflexed, pushing into substrate after anthesis, fertile flowers 2–7, sterile flowers 0–80, globose or cylindric, 0.5–1.5 × 0.8–1.5 cm; involucres absent. |
Peduncles | 1–12 cm. |
2–6.5 cm. |
Pedicels | absent; bracteoles lanceolate, 6–7 mm, acuminate. |
reflexed after anthesis, 0.2–0.4 mm; bracteoles absent. |
Flowers | 12–16 mm; calyx urceolate, not bilabiate, inflated in fruit, 6–10 mm, glabrous, veins 20–36, connected by transverse veins in fruit, tube 3–5 mm, lobes reflexed, subequal, subulate, as long as tube, orifice constricted; corolla white becoming pink, 12–15 mm, banner ovate, broadly clawed, striate, 12–15 × 2–4 mm, apex acute-acuminate. |
fertile ones 7–15 mm; calyx tubular, 5–6 mm, glabrous or hairy, veins indistinct, tube 3–4 mm, lobes subequal, pubescent or glabrous, spreading, orifice open; corolla white, pink, or pink-striped, 7–10 mm, banner ovate-elliptic, 7–10 × 1.5–2 mm, apex rounded; sterile flowers 4–7 mm; calyx teeth linear; corolla absent. |
Legumes | ellipsoid, 2.5–2.5 mm, shorter than calyx. |
subterranean, obovoid, 3–4 mm. |
Seeds | 2 or 3, brown, ovoid, 1–1.5 mm, roughened. |
1, purplish black, ellipsoid, 2.6–3 mm, smooth, dull. |
2n | = 16. |
= 16. |
Trifolium vesiculosum |
Trifolium subterraneum |
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Phenology | Flowering Apr–Jul. | Flowering Mar–May. |
Habitat | Fields, roadsides, forest openings. | Open, disturbed sandy soils. |
Elevation | 0–1000 m. (0–3300 ft.) | 0–1000 m. (0–3300 ft.) |
Distribution |
AL; AR; CA; FL; GA; LA; MA; MO; MS; OK; OR; SC; TX; VA; WA; s Europe; e Europe; w Asia [Introduced in North America]
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CA; GA; LA; MA; MS; NC; NJ; OR; SC; WA; BC; w Europe; w Asia; n Africa [Introduced in North America; introduced also in s South America, s Africa, Pacific Islands (Hawaii, New Zealand), Australia]
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Discussion | Trifolium vesiculosum was first introduced into cultivation in the United States in 1963 and is grown in southern and western states (J. D. Miller and H. D. Wells 1985). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Trifolium subterraneum was first introduced by the USDA about 1921 as a pasture crop; it is utilized as such in the western and southern United States (W. S. McGuire 1985). Inflorescences of T. subterraneum consist of intermixed sterile and fertile flowers; after fetilization, the inflorescence is pushed underground, where the fruits develop. (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 | ||
Name authority | Savi: Fl. Pis. 2: 165. (1798) — (as vessiculosum) | Linnaeus: Sp. Pl. 2: 767. (1753) |
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