Trifolium subterraneum |
Trifolium angustifolium |
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burrowing clover, subclover, subterranean clover, subterranean trefoil |
narrow-leaf clover, narrow-leaf crimson clover |
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Habit | Herbs annual, 10–80 cm, glabrous or appressed-pubescent. | Herbs annual, 10–30 cm, appressed-pubescent. |
Stems | prostrate to ascending, branched. |
erect, unbranched to sparsely branched. |
Leaves | 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. |
palmate; stipules lanceolate to linear, 0.5–2.2 cm, margins entire, apex lanceolate-linear; petiole 2–3 cm; petiolules 1+ mm; leaflets 3, blades linear-lanceolate, 3–5 × 0.2–0.4 cm, base cuneate, veins fine, margins entire, apex acute, surfaces hairy. |
Inflorescences | 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. |
terminal, 25–75-flowered, spicate, cylindric or conic, 3–8 × 1.5–2 cm; involucres absent. |
Peduncles | 2–6.5 cm. |
1–2.2 cm. |
Pedicels | reflexed after anthesis, 0.2–0.4 mm; bracteoles absent. |
erect, 0.5 mm; bracteoles absent. |
Flowers | 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. |
10–13 mm; calyx tubular, 8–13 mm, tuberculate with appressed, stiff hairs, veins 10, tube 3–5 mm, lobes unequal, abaxial lobes longest, subulate-setaceous, spreading stellate in fruit, orifice closed by bilabiate callosities, hairy; corolla usually pale pink or purple, rarely white, 9–12 mm, banner ovate-elliptic, 9–12 × 2–2.5 mm, apex notched. |
Legumes | subterranean, obovoid, 3–4 mm. |
ovoid, leathery distally, transversely dehiscent, 2.2–2.5 mm. |
Seeds | 1, purplish black, ellipsoid, 2.6–3 mm, smooth, dull. |
1, light brown or yellow, ovoid, 1.6–2 mm, smooth, glossy. |
2n | = 16. |
= 14, 16. |
Trifolium subterraneum |
Trifolium angustifolium |
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Phenology | Flowering Mar–May. | Flowering Mar–Apr. |
Habitat | Open, disturbed sandy soils. | Waste places, fields, meadows. |
Elevation | 0–1000 m. (0–3300 ft.) | 0–1000 m. (0–3300 ft.) |
Distribution |
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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AL; CA; OR; SC; Europe; w Asia; n Africa; Atlantic Islands (Canary Islands) [Introduced in North America; introduced also in s South America (Chile, Uruguay), s Africa, Pacific Islands (New Zealand), Australia]
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Discussion | 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.) |
Trifolium angustifolium is spreading rapidly in west-central California and is weedy in many regions globally (R. P. Randall 2002). (Discussion copyrighted by Flora of North America; reprinted with permission.) |
Source | FNA vol. 11. | FNA vol. 11. |
Parent taxa | ||
Sibling taxa | ||
Name authority | Linnaeus: Sp. Pl. 2: 767. (1753) | Linnaeus: Sp. Pl. 2: 769. (1753) |
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