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least hop clover, lesser hop clover, lesser hop trefoil, little hop clover, shamrock, small hop-clover, suckling clover

pin point clover, slender clover

Habit Herbs annual, 20–40 cm, glabrous or sparsely hairy. Herbs annual, 2–60 cm, glabrous.
Stems

erect to prostrate, branched from base.

erect or ascending, branched.

Leaves

pinnate;

stipules ovate, 0.3–0.5 cm, margins entire, apex acute;

petiole to 1.5 cm;

lateral leaflet petiolules to 0.5 mm, terminal leaflet stalk 1–1.5 mm;

leaflets 3, blades obovate to elliptic-lanceolate, 1–2 × 0.5–1.5 cm, base cuneate, lateral veins prominent, ± parallel, ascending, margins dentate distally, apex rounded or retuse, surfaces glabrous or sparsely hairy.

palmate;

stipules ovate-lanceolate, 0.5–2.5 cm, membranous, margins entire or slightly serrate, apex long-acuminate;

petiole 0.5–9 cm;

petiolules to 0.5 mm;

leaflets 3, blades obovate to obcordate, 0.5–2.5 × 0.2–1.5 cm, base cuneate, veins moderately thickened, margins setose-serrulate, apex rounded, shallowly retuse, surfaces glabrous.

Inflorescences

axillary or terminal, 5–20-flowered, ovoid or globose, 0.5–0.9 × 0.6 cm;

involucres absent.

axillary or terminal, 10–25-flowered, globose to subglobose, 0.5–2 × 0.5–2 cm, rachis prolonged beyond flowers;

involucres a narrow, membranous, dentate rim, to 0.5 mm.

Peduncles

1–1.5 cm.

1–9 cm.

Pedicels

reflexed, 0.2–0.5 mm;

bracteoles a fringe of red setae.

becoming dramatically reflexed, 3–4 mm;

bracteoles low, cuplike, membranous, to 0.5 mm.

Flowers

2.8–3.5 mm;

calyx campanulate, 1.5–2 mm, glabrous, veins 5, tube 0.8–1 mm, lobes unequal, longer than tube, adaxial 2 shorter, orifice open;

corolla pale yellow becoming brown, 2.6–3.2 mm, not or slightly ribbed, banner persistent, spatulate, 2.6–3.2 × 2 mm, apex rounded to broadly acute.

5–7.5 mm;

calyx narrowly campanulate, 4.5–6.5 mm, glabrous, veins 10, tube 2–2.5 mm, lobes unequal, long-triangular, margins green or purple, orifice open;

corolla white, pink, or purple, 5–8 mm, banner ovate, 5–8 × 3–4 mm, apex broadly rounded, retuse or apiculate.

Legumes

stipitate, ellipsoid, 1.5–2 mm, short beaked.

ovoid-ellipsoid, 4–6 mm.

Seeds

1, yellow or pale brown, ellipsoid, 0.9–1 mm, smooth, glossy.

1 or 2, tan to brown, mitten-shaped, 1.1–1.5 mm, smooth.

2n

= 16, 28, 32.

= 16.

Trifolium dubium

Trifolium gracilentum

Phenology Flowering May–Oct. Flowering Mar–Jun.
Habitat Disturbed ground, fields. Open, grassy areas, gravelly ridges, roadsides, adobe slopes, moist places.
Elevation 0–2300 m. (0–7500 ft.) 50–1200 m. (200–3900 ft.)
Distribution
from FNA
AK; AL; AR; AZ; CA; CT; DC; DE; FL; GA; IA; ID; IL; IN; KS; KY; LA; MA; MD; ME; MI; MN; MO; MS; MT; NC; ND; NE; NH; NJ; NM; NV; NY; OH; OK; OR; PA; RI; SC; TN; TX; VA; VT; WA; WI; WV; WY; BC; NB; NS; ON; PE; QC; SPM; c Europe; s Europe; w Asia [Introduced in North America; introduced also in s South America, e Asia (e China), n, s Africa, Pacific Islands (Hawaii, New Zealand), Australia]
[WildflowerSearch map]
[BONAP county map]
from FNA
AZ; CA; NV; OR; WA; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
Discussion

Trifolium dubium is often confused with Medicago lupulina Linnaeus; the latter may be distinguished by its toothed stipules, deciduous corollas, and shiny, black fruits. Little hop clover may be the co-called shamrock of Irish folklore (E. C. Nelson 1991; P. S. Wyse Jackson 2014); other candidates include other species of Trifolium or species of Medicago or Oxalis.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Abundance of Trifolium gracilentum increases in response to burns (J. M. DiTomaso et al. 1999).

The record of Trifolium gracilentum from South Carolina is a waif.

(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. 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. 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. 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. vesiculosum, T. virginicum, T. willdenovii, T. wormskioldii
Synonyms Chrysaspis dubia, T. minus T. denudatum, T. exile, T. gracilentum var. exile, T. gracilentum var. inconspicuum, T. gracilentum var. reductum, T. inconspicuum
Name authority Sibthorp: Fl. Oxon., 231. (1794) Torrey & A. Gray: Fl. N. Amer. 1: 316. (1838)
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