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

woolly clover

Habit Herbs annual, 20–40 cm, glabrous or sparsely hairy. Herbs annual, 10–20 cm, glabrous or sparsely hairy.
Stems

erect to prostrate, branched from base.

prostrate, ascending, or erect, 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 or triangular-lanceolate, 0.4–1.2 cm, margins entire, apex acute or acuminate;

petiole 0.5–7 cm;

petiolules to 1 mm;

leaflets 3, blades obovate, obcordate, or elliptic, 0.4–1.5 × 0.3–1 cm, base cuneate, veins moderately prominent, margins denticulate, apex rounded or emarginate, surfaces sparsely hairy abaxially, glabrous adaxially.

Inflorescences

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

involucres absent.

axillary, 10–20-flowered, subglobose, soon becoming globose, flowers resupinate, calyces densely white-woolly, compacted, inflated, 0.5–1.5 × 0.5–1.5 cm;

involucres a narrow rim, 0.2 mm.

Peduncles

1–1.5 cm.

0.5–1.5 cm.

Pedicels

reflexed, 0.2–0.5 mm;

bracteoles a fringe of red setae.

slightly reflexed, to 0.5 mm;

bracteoles cup-shaped, membranous, 0.2 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.

3–7 mm;

calyx tubular, inflated in fruit, markedly asymmetric-bilabiate, 2–6 mm, woolly adaxially, veins 5–10, connected by lateral veins, tube 1.5–2.5 mm, 4–5 mm in fruit, lobes unequal, subulate, shorter than tube, adaxial spreading or curved, orifice open, abruptly constricted in fruit;

corolla pink, 3–6 mm, banner ovate, 3–6 × 3–6 mm, apex emarginate to crenulate.

Legumes

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

ovoid to globose, 2–3 mm.

Seeds

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

1 or 2, yellow to brown, mottled, mitten-shaped, 0.9–1.1 mm, smooth, glossy.

2n

= 16, 28, 32.

= 16.

Trifolium dubium

Trifolium tomentosum

Phenology Flowering May–Oct. Flowering Feb–Apr.
Habitat Disturbed ground, fields. Sandy lawns, fields, meadows, roadsides, clay soils among vernal pools.
Elevation 0–2300 m. (0–7500 ft.) 0–400 m. (0–1300 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
CA; FL; MA; NC; SC; s Europe (Mediterranean); sw Asia; n Africa; Atlantic Islands (Azores) [Introduced in North America; introduced also in South America (Chile), s Africa, Pacific Islands (New Zealand), Australia]
[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.)

Trifolium tomentosum is occasionally cultivated as a forage crop (F. J. Hermann 1953) and is becoming weedy in the flora area and in Australia (R. P. Randall 2002).

(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. 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. trichocalyx, T. variegatum, T. vesiculosum, T. virginicum, T. willdenovii, T. wormskioldii
Synonyms Chrysaspis dubia, T. minus
Name authority Sibthorp: Fl. Oxon., 231. (1794) Linnaeus: Sp. Pl. 2: 771. (1753)
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