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small-head clover

thimble clover, Valparaiso clover

Habit Herbs annual, 3–55 cm, densely to sparsely pubescent. Herbs annual, 6–35 cm, villous or glabrous.
Stems

erect to ascending, branched.

erect or ascending, branched.

Leaves

palmate;

stipules obliquely ovate, 0.4–1.2 cm, margins entire or slightly serrate, apex acuminate;

petiole 1–5 cm;

petiolules 0.5 mm;

leaflets 3, blades oblanceolate, obovate, or obcordate, 0.4–1.7 × 0.3–1.1 cm, base cuneate, veins fine or slightly thickened, margins setose, often dentate distally, apex usually retuse, rarely rounded, surfaces villous.

palmate;

stipules obliquely ovate, 0.4–1.2 cm, margins entire, toothed, or lacerate, apex acuminate;

petiole 1–8 cm;

petiolules 0.5 mm;

leaflets 3, blades obovate or obcordate, 0.4–1.4 × 0.3–1.2 cm, base cuneate, veins fine, thickened distally, margins serrate, apex rounded or emarginate, surfaces villous or glabrous.

Inflorescences

axillary or terminal, 10–40-flowered, globose, 0.5–1.3 × 0.4–1.2 cm;

involucres flattened or bowl-shaped, 0.4–1 cm, when folded, nearly completely hiding calyces, villous, incised 1/2 their length, lobes 5–12, lanceolate-ovate, entire or slightly toothed proximally, acuminate.

axillary or terminal, 10–17-flowered, subglobose, 0.8–1.7 × 0.5–1.5 cm;

involucres cup-shaped, 0.5–1.5 cm, glabrous or sparsely hairy, lobes 8–12, ovate, conspicuously sharply toothed.

Peduncles

1–8 cm.

1.5–7.4 cm.

Pedicels

absent;

bracteoles absent.

absent;

bracteoles absent.

Flowers

4–6 mm;

calyx campanulate-tubular, 3–5.5 mm, pubescent, veins 10, tube 1.8–2.5 mm, lobes ± equal, triangular-aristate, margins hyaline, wavy, orifice open;

corolla white or pink to lavender, 4–6 mm, banner oblong, 3–6 × 1–2 mm, apex emarginate.

6–7 mm;

calyx tubular-campanulate, 3–4 mm, glabrous, veins 10, tube 2.5–3.5 mm, lobes ± equal, triangular, not or minutely aristate, conspicuously toothed, margins membranous, orifice open;

corolla pale pink or white, 6–9 mm, banner oblong, 6–9 × 2–3 mm, apex narrowly rounded or emarginate-mucronate.

Legumes

broadly ellipsoid, 1.5–2 mm.

ovoid, 2–3 mm.

Seeds

1, yellow, reddish mottled, oblong, 1.5 mm, smooth.

1 or 2, greenish, sometimes mottled, oblong, 1.5–2 mm, smooth.

2n

= 16.

= 16.

Trifolium microcephalum

Trifolium microdon

Phenology Flowering Mar–Jul. Flowering Apr–Jul.
Habitat Meadows, roadsides, stream banks, forest clearings, grassy slopes. Meadows, roadsides, dry slopes, fields, open oak or pine forests.
Elevation 0–2500 m. (0–8200 ft.) 0–1500 m. (0–4900 ft.)
Distribution
from FNA
AK; AZ; CA; ID; MT; NV; OR; WA; BC; Mexico (Baja California)
[WildflowerSearch map]
[BONAP county map]
from FNA
CA; ID; OR; WA; BC; Mexico (Baja California); South America (Chile)
[WildflowerSearch map]
[BONAP county map]
Discussion

Trifolium microcephalum is common in much of its range in California and northward into Oregon, and is rare in much of the rest of its range. It is closely allied with the Chilean T. vernum Philippi (N. W. Ellison et al. 2006), which it resembles greatly, and from which it is distinguished by its shorter calyx lobes (M. Zohary and D. Heller 1984).

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

Trifolium microdon is one of several clovers that have an apparently natural disjunct distribution between the western coast of South America (Chile) and western North America. Others include T. depauperatum var. depauperatum and T. macraei.

In herbarium specimens of Trifolium microdon, the folded involucre hides, or nearly hides, the calyces, whereas in herbarium specimens of similar T. microcephalum, the calyces are still visible.

(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. 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. 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 Lojaconoa microcephala, T. microcephalum var. bipedale, T. microcephalum var. lemmonii T. microdon var. pilosum
Name authority Pursh: Fl. Amer. Sept. 2: 478. (1813) Hooker & Arnott: Bot. Misc. 3: 180. (1833)
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