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olive clover

thimble clover, Valparaiso clover

Habit Herbs annual, 8–30 cm, canescent. Herbs annual, 6–35 cm, villous or glabrous.
Stems

erect, branched from base and distally, or unbranched.

erect or ascending, branched.

Leaves

palmate;

stipules ovate, 0.4–1.2 cm, margins entire, ciliate, apex often purple, acuminate, setaceous;

petiole 0.5–8 cm;

petiolules 0.5–1 mm;

leaflets 3, blades obovate or elliptic, 0.5–3 × 0.3–1.2 cm, base cuneate, veins obscure or slightly thickened, margins dentate, apex rounded or emarginate, surfaces pilose.

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

terminal or axillary, 25–50-flowered, ovoid-ellipsoid, 1–2.5 × 1.2–2.5 cm;

involucres absent.

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

3–11 cm.

1.5–7.4 cm.

Pedicels

absent;

bracteoles cuplike, to 0.5 mm.

absent;

bracteoles absent.

Flowers

6–10 mm;

calyx tubular, 8–14 mm, densely pubescent, veins 20–30, tube 1–2 mm, lobes nearly equal, appearing rigidly erect, linear-setaceous, plumose, sinuses acute, orifice open;

corolla sometimes absent, red-violet, often with white tips, 4–6 mm, banner ovate-oblong, 7–8 × 2–3 mm, apex broadly rounded, apiculate.

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

obovoid, 3–3.5 mm.

ovoid, 2–3 mm.

Seeds

1, yellow-brown, ellipsoid, 2–2.5 mm, smooth.

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

2n

= 16.

Trifolium columbinum

Trifolium microdon

Phenology Flowering Apr–May. Flowering Apr–Jul.
Habitat Grassy slopes, meadows, heavy adobe/clay soils, oak woodland foothills. Meadows, roadsides, dry slopes, fields, open oak or pine forests.
Elevation 0–1400 m. (0–4600 ft.) 0–1500 m. (0–4900 ft.)
Distribution
from FNA
CA
from FNA
CA; ID; OR; WA; BC; Mexico (Baja California); South America (Chile)
[WildflowerSearch map]
[BONAP county map]
Discussion

D. Isely (1998) stated that Central Valley populations of Trifolium columbinum appeared to be extinct and populations outside that region (and here recognized as the same taxon) were similar in calyx and corolla proportions. It is rather widespread in California, ranging from Humboldt County southward to Santa Barbara County, and eastward into counties ranging from Shasta southward to Inyo, Kern, and Placer counties.

Trifolium albopurpureum var. olivaceum (Greene) Isely and T. columbinum var. olivaceum (Greene) Jepson are illegitimate names that pertain here (D. J. Keil 2019).

(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. 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
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 T. albopurpureum var. columbinum, T. columbinum var. argillorum, T. olivaceum, T. olivaceum var. columbinum, T. olivaceum var. griseum T. microdon var. pilosum
Name authority Greene: Pittonia 1: 4. (1887) Hooker & Arnott: Bot. Misc. 3: 180. (1833)
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