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

Anderson's clover, fiveleaf clover

Habit Herbs annual, 20–40 cm, glabrous or sparsely hairy. Herbs perennial, 5–12 cm, canescent.
Stems

erect to prostrate, branched from base.

erect-ascending, cespitose, mat-forming, branched;

from deep taproot-like crown.

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 lanceolate, 0.5–1.5 cm, margins entire, apex long-acuminate;

petiole 1–5 cm;

petiolules to 0.5 mm;

leaflets (3–)5, blades obovate, 0.5–2.2 × 0.2–1.2 cm, base cuneate, veins obscured by pubescence, margins entire, apex rounded or acute, apiculate, surfaces canescent.

Inflorescences

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

involucres absent.

axillary, 10–20-flowered, depressed-globose, 1–2 × 1–2.3 cm;

involucres formed of connate, narrow, membranous bracts, to 0.5 mm.

Peduncles

1–1.5 cm.

1–14 cm.

Pedicels

reflexed, 0.2–0.5 mm;

bracteoles a fringe of red setae.

absent;

bracteoles absent.

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.

10–17 mm;

calyx campanulate, 9–11 mm, pilose, veins 10, tube 4–5 mm, lobes equal, subulate, plumose, orifice open;

corolla white or pink, 10–17 mm, banner ovate-oblong, 12–19 × 3–5 mm, apex rounded, retuse.

Legumes

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

ellipsoid, 4–5 mm.

Seeds

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

1 (or 2), tan or brown, irregularly ovoid, 1.6–2 mm, smooth, glossy.

2n

= 16, 28, 32.

Trifolium dubium

Trifolium andersonii

Phenology Flowering May–Oct.
Habitat Disturbed ground, fields.
Elevation 0–2300 m. (0–7500 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 USDA
w United States
[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.)

Subspecies 3 (3 in the flora).

Trifolium andersonii encompasses three moderately well separable subspecies, with subsp. andersonii the more northern form in the range of the species, subsp. monoense in the southwestern portion of the range, and subsp. beatleyae in the eastern portion of the range (J. M. Gillett 1972). Intermediates between the latter two (and overlap in their ranges) make differentiation between them somewhat problematic, which prompted R. C. Barneby (1989) to combine them as var. beatleyae.

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

Key
1. Leaflet blades 0.5–1.1 cm, surfaces with appressed hairs to l mm; 3000–4000 m.
subsp. monoense
1. Leaflet blades 0.9–2.2 cm, surfaces with spreading hairs 1.5–2 mm; 800–2500 m.
→ 2
2. Peduncles l–3 cm, not overtopping leaves.
subsp. andersonii
2. Peduncles 4–14 cm, overtopping leaves.
subsp. beatleyae
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. 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. vesiculosum, T. virginicum, T. willdenovii, T. wormskioldii
Subordinate taxa
T. andersonii subsp. andersonii, T. andersonii subsp. beatleyae, T. andersonii subsp. monoense
Synonyms Chrysaspis dubia, T. minus
Name authority Sibthorp: Fl. Oxon., 231. (1794) A. Gray: Proc. Amer. Acad. Arts 6: 522. (1865)
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