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burrowing clover, subclover, subterranean clover, subterranean trefoil

few-flower clover, few-flowerered clover

Habit Herbs annual, 10–80 cm, glabrous or appressed-pubescent. Herbs annual, 10–50 cm, glabrous.
Stems

prostrate to ascending, branched.

erect, dichotomously 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, 0.4–1.2 cm, margins lacerate, apex subulate;

petiole 0.5–4 cm;

petiolules to 0.5 mm;

leaflets 3, blades linear, oblong, oblanceolate, or elliptic, 0.5–2.5 × 0.1–0.5 cm, base cuneate, veins fine or moderately thickened, margins entire, spinulose, or dentate, apex rounded or truncate, mucronate, surfaces glabrous.

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.

axillary or terminal, 3–15-flowered, obconic, 0.3–1.2 × 0.3–0.8 cm;

involucres flattened to bowl-shaped, 1–2 mm, when folded, not hiding flowers except proximally, incised 4/5–9/10 their length, lobes lanceolate-subulate.

Peduncles

2–6.5 cm.

2.5–7.5 cm.

Pedicels

reflexed after anthesis, 0.2–0.4 mm;

bracteoles absent.

erect, 0.5–2 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.

11–16 mm;

calyx campanulate, slit between adaxial lobes, 4–5 mm, glabrous, veins 10, tube 2.5–5.2 mm, lobes triangular-subulate, 3-fid or shouldered below apex, orifice open;

corolla lavender with white tips, keel petals purple, 6–8 mm, banner narrowly ovate-oblong, 6–8 × 2 mm, apex narrowly rounded, erose.

Legumes

subterranean, obovoid, 3–4 mm.

sessile, oblong, 2.1–3.2 mm.

Seeds

1, purplish black, ellipsoid, 2.6–3 mm, smooth, dull.

1 or 2 (or 3), reddish brown, mottled, lenticular or reniform, 1.2–1.3 mm, smooth.

2n

= 16.

= 16.

Trifolium subterraneum

Trifolium oliganthum

Phenology Flowering Mar–May. Flowering Mar–Jul.
Habitat Open, disturbed sandy soils. Stream banks, grassy, rocky slopes, meadows, fields.
Elevation 0–1000 m. (0–3300 ft.) 0–1100 m. (0–3600 ft.)
Distribution
from FNA
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]
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; OR; WA; BC
[WildflowerSearch map]
[BONAP county map]
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 oliganthum is relatively common throughout much of its range in California; it is found in a few scattered sites northward into Oregon, Washington, and British Columbia. Even though it closely resembles T. variegatum, it is placed near T. bifidum in molecular studies (N. W. Ellison et al. 2006).

Trifolium hexanthum Greene ex A. Heller, which pertains here, is not a validly published name.

(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
T. albopurpureum, T. alexandrinum, T. amoenum, T. amphianthum, T. andersonii, T. andinum, T. angustifolium, T. appendiculatum, T. arvense, T. attenuatum, T. aureum, T. barbigerum, T. barnebyi, T. beckwithii, T. bejariense, T. bifidum, T. bolanderi, T. brandegeei, T. breweri, T. buckwestiorum, T. calcaricum, T. campestre, T. carolinianum, T. cernuum, T. ciliolatum, T. columbinum, T. cyathiferum, T. dasyphyllum, T. dedeckerae, T. depauperatum, T. dichotomum, T. douglasii, T. dubium, T. echinatum, T. eriocephalum, T. fragiferum, T. friscanum, T. fucatum, T. glomeratum, T. gracilentum, T. grayi, T. gymnocarpon, T. haydenii, T. hirtum, T. howellii, T. hybridum, T. hydrophilum, T. incarnatum, T. jokerstii, T. kentuckiense, T. kingii, T. lappaceum, T. latifolium, T. leibergii, T. lemmonii, T. longipes, T. lupinaster, T. macilentum, T. macraei, T. macrocephalum, T. medium, T. microcephalum, T. microdon, T. monanthum, T. mucronatum, T. nanum, T. nigrescens, T. obtusiflorum, T. oliganthum, T. ornithopodioides, T. owyheense, T. palmeri, T. parryi, T. pinetorum, T. piorkowskii, T. plumosum, T. polyodon, T. pratense, T. productum, T. reflexum, T. repens, T. resupinatum, T. retusum, T. rollinsii, T. siskiyouense, T. sonorense, T. stoloniferum, T. striatum, T. suffocatum, T. thompsonii, T. tomentosum, T. trichocalyx, T. variegatum, T. vesiculosum, T. virginicum, T. willdenovii, T. wormskioldii
T. albopurpureum, T. alexandrinum, T. amoenum, T. amphianthum, T. andersonii, T. andinum, T. angustifolium, T. appendiculatum, T. arvense, T. attenuatum, T. aureum, T. barbigerum, T. barnebyi, T. beckwithii, T. bejariense, T. bifidum, T. bolanderi, T. brandegeei, T. breweri, T. buckwestiorum, T. calcaricum, T. campestre, T. carolinianum, T. cernuum, T. ciliolatum, T. columbinum, T. cyathiferum, T. dasyphyllum, T. dedeckerae, T. depauperatum, T. dichotomum, T. douglasii, T. dubium, T. echinatum, T. eriocephalum, T. fragiferum, T. friscanum, T. fucatum, T. glomeratum, T. gracilentum, T. grayi, T. gymnocarpon, T. haydenii, T. hirtum, T. howellii, T. hybridum, T. hydrophilum, T. incarnatum, T. jokerstii, T. kentuckiense, T. kingii, T. lappaceum, T. latifolium, T. leibergii, T. lemmonii, T. longipes, T. lupinaster, T. macilentum, T. macraei, T. macrocephalum, T. medium, T. microcephalum, T. microdon, T. monanthum, T. mucronatum, T. nanum, T. nigrescens, T. obtusiflorum, T. ornithopodioides, T. owyheense, T. palmeri, T. parryi, T. pinetorum, T. piorkowskii, T. plumosum, T. polyodon, T. pratense, T. productum, T. reflexum, T. repens, T. resupinatum, T. retusum, T. rollinsii, T. siskiyouense, T. sonorense, T. stoloniferum, T. striatum, T. subterraneum, T. suffocatum, T. thompsonii, T. tomentosum, T. trichocalyx, T. variegatum, T. vesiculosum, T. virginicum, T. willdenovii, T. wormskioldii
Synonyms T. pauciflorum, T. filipes, T. oliganthum var. sonomense, T. triflorum
Name authority Linnaeus: Sp. Pl. 2: 767. (1753) Steudel: Nomencl. Bot. ed. 2, 2: 707. (1841)
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