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arrow-leaf clover

burrowing clover, subclover, subterranean clover, subterranean trefoil

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

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
from FNA
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]
[WildflowerSearch map]
[BONAP county map]
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]
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
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. subterraneum, T. suffocatum, T. thompsonii, T. tomentosum, T. trichocalyx, T. variegatum, 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. 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
Name authority Savi: Fl. Pis. 2: 165. (1798) — (as vessiculosum) Linnaeus: Sp. Pl. 2: 767. (1753)
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