Trifolium eriocephalum |
Trifolium subterraneum |
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woolly-head clover |
burrowing clover, subclover, subterranean clover, subterranean trefoil |
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Habit | Herbs perennial, 12–46 cm, sparsely hairy to densely villous, appressed-pubescent, or glabrate. | Herbs annual, 10–80 cm, glabrous or appressed-pubescent. | ||||||||||||||||||||
Stems | erect or decumbent, branched. |
prostrate to ascending, branched. |
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Leaves | palmate; stipules lanceolate or ovate, 1–5 cm, margins entire or denticulate, apex acuminate or acute; petiole 1–15 cm; petiolules 1 mm; leaflets 3, blades linear, linear-elliptic, elliptic, lanceolate, lanceolate-oblong, or obovate, 1–5 × 0.4–1.2 cm, base cuneate, veins fine or ± thickened, margins denticulate or serrulate, apex acuminate or acute, surfaces appressed-pubescent abaxially, glabrous, densely villous, or sparsely or densely pilose adaxially. |
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. |
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Inflorescences | terminal or axillary, 25–70-flowered, inverted or horizontal, ellipsoid or globose to subglobose, 2–3 × 1–3 cm, rachis prolonged beyond flowers; 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. |
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Peduncles | bent distally, proximal to flowers, 3–18 cm. |
2–6.5 cm. |
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Pedicels | reflexed, to 0.3 mm; bracteoles absent. |
reflexed after anthesis, 0.2–0.4 mm; bracteoles absent. |
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Flowers | 9–18 mm; calyx campanulate, curved in fruit, 4–11 mm, villous, veins 10, tube 1.5–2.5 mm, lobes unequal, 2–3 times tube, subulate, often strongly curved and twisted, plumose, orifice open; corolla white, cream, or purple, 8–16 mm, banner oblanceolate, 8–16 × 3–5 mm, apex rounded or retuse, recurved; ovaries pubescent distally. |
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. |
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Legumes | ovoid, 2–3.5 mm. |
subterranean, obovoid, 3–4 mm. |
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Seeds | (1 or)2–4, yellow-brown to brown, mitten-shaped or subglobose, 1.2–2 mm, smooth. |
1, purplish black, ellipsoid, 2.6–3 mm, smooth, dull. |
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2n | = 16. |
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Trifolium eriocephalum |
Trifolium subterraneum |
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Phenology | Flowering Mar–May. | |||||||||||||||||||||
Habitat | Open, disturbed sandy soils. | |||||||||||||||||||||
Elevation | 0–1000 m. [0–3300 ft.] | |||||||||||||||||||||
Distribution |
w United States
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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 | Subspecies 6 (6 in the flora). Trifolium eriocephalum was revised by J. M. Gillett (1971). The subspecies exhibit unusually complex distributional patterns, and overlapping morphological features sometimes make identifications problematic (M. Zohary and D. Heller 1984). (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.) |
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Key |
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Source | FNA vol. 11. | FNA vol. 11. | ||||||||||||||||||||
Parent taxa | ||||||||||||||||||||||
Sibling taxa | ||||||||||||||||||||||
Subordinate taxa | ||||||||||||||||||||||
Name authority | Nuttall in J. Torrey and A. Gray: Fl. N. Amer. 1: 313. (1838) | Linnaeus: Sp. Pl. 2: 767. (1753) | ||||||||||||||||||||
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