Trifolium macrocephalum |
Trifolium subterraneum |
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big-head clover, large-head clover |
burrowing clover, subclover, subterranean clover, subterranean trefoil |
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Habit | Herbs perennial, 5–25 cm, villous. | Herbs annual, 10–80 cm, glabrous or appressed-pubescent. |
Stems | erect or ascending, branched. |
prostrate to ascending, branched. |
Leaves | palmate; stipules ovate, obovate, or oblong, 1–3 cm, margins entire, irregularly lobed, or serrate, apex acute or acuminate; petiole 1–14 cm; petiolules 0.9–1.2 mm; leaflets (5–)7–9, blades broadly to narrowly obovate, often folded, 1–2.7 × 0.4–1.1 cm, base cuneate, veins thickened, especially distally, margins serrulate, apex rounded or truncate, apiculate, surfaces villous abaxially, sparsely villous to glabrate 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. |
Inflorescences | terminal, 20–32-flowered, globose or ovoid-ellipsoid, 2.5–8 × 3–7 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 | 2–8 cm. |
2–6.5 cm. |
Pedicels | erect, 1–1.5 mm; bracteoles broadly ovate, membranous, to 0.5 mm, truncate. |
reflexed after anthesis, 0.2–0.4 mm; bracteoles absent. |
Flowers | 20–30 mm; calyx campanulate, 10–22 mm, villous, veins 10–15, tube 2.5–4 mm, lobes subequal, subulate, plumose, orifice open; corolla white, creamy white, or pinkish, keel petals deep pink, 20–28 mm, banner ovate or oblong, 20–28 × 10–13 mm, apex rounded or slightly emarginate. |
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 | ovoid, 4–5 mm. |
subterranean, obovoid, 3–4 mm. |
Seeds | 1 or 2, yellow or reddish, mitten-shaped to ellipsoid, 2.5–3 mm, smooth. |
1, purplish black, ellipsoid, 2.6–3 mm, smooth, dull. |
2n | = 32, 48. |
= 16. |
Trifolium macrocephalum |
Trifolium subterraneum |
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Phenology | Flowering Apr–Jun. | Flowering Mar–May. |
Habitat | Rocky places, hard, compacted clay-gumbo, lava beds, sage-covered slopes, full sun. | Open, disturbed sandy soils. |
Elevation | 80–2500 m. [260–8200 ft.] | 0–1000 m. [0–3300 ft.] |
Distribution |
CA; ID; NV; OR; WA
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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 macrocephalum has the largest inflorescences of any clover. Trifolium megacephalum Nuttall (1818) is an illegitimate replacement name for Lupinaster macrocephalum Pursh. (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 | ||
Sibling taxa | ||
Synonyms | Lupinaster macrocephalum | |
Name authority | (Pursh) Poiret in J. Lamarck et al.: Encycl., suppl. 5: 336. (1817) | Linnaeus: Sp. Pl. 2: 767. (1753) |
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