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big-head clover, large-head clover

marshmallow clover, Piorkowski's clover

Habit Herbs perennial, 5–25 cm, villous. Herbs annual, 7–30 cm, glabrous.
Stems

erect or ascending, branched.

erect or ascending, sparsely to much branched.

Leaves

palmate;

stipules ovate, obovate, or oblong, 1–3 cm, margins entire, irregularly lobed, or serrate, apex acute or acuminate;

petiole 1–14 cm;

petiolules 0.9–1.2 mm;

leaflets (5–)7–9, blades broadly to narrowly obovate, often folded, 1–2.7 × 0.4–1.1 cm, base cuneate, veins thickened, especially distally, margins serrulate, apex rounded or truncate, apiculate, surfaces villous abaxially, sparsely villous to glabrate adaxially.

palmate;

stipules ovate-lanceolate, 1–1.5 cm, margins entire, apex acute-acuminate;

petiole 8–12 cm;

petiolules 1 mm;

leaflets 3, blades oblanceolate or obovate, 2.8 × 1.9 cm, base cuneate, veins delicate, margins entire or shallowly dentate distally, lateral veins sometimes ending in a bristle, apex rounded to acute, surfaces glabrous.

Inflorescences

terminal, 20–32-flowered, globose or ovoid-ellipsoid, 2.5–8 × 3–7 cm;

involucres absent.

axillary or terminal, 3–16-flowered, in 1–3 whorls, subglobose, 2–2.8 × 1.8–2.6 cm;

involucres bowl-shaped, 6–15 mm, lobes 6–8, broadly lanceolate, margins entire, acuminate, apex 3–5-fid.

Peduncles

2–8 cm.

5–15 cm.

Pedicels

erect, 1–1.5 mm;

bracteoles broadly ovate, membranous, to 0.5 mm, truncate.

straight, 0.5–1 mm;

bracteoles absent.

Flowers

20–30 mm;

calyx campanulate, 10–22 mm, villous, veins 10–15, tube 2.5–4 mm, lobes subequal, subulate, plumose, orifice open;

corolla white, creamy white, or pinkish, keel petals deep pink, 20–28 mm, banner ovate or oblong, 20–28 × 10–13 mm, apex rounded or slightly emarginate.

12–14 mm;

calyx campanulate, 5–8 mm, glabrous, veins 10, tube 2.5–4 mm, lobes 11–15, unequal, abaxial 3–5 forked, adaxial unbranched, orifice open;

corolla creamy white to pinkish, 11–13 mm, banner ovate, inflated entire length in fruit, not distally twisted, 11–13 × 5–7 mm, apex rounded.

Legumes

ovoid, 4–5 mm.

ellipsoid, 5–6 mm.

Seeds

1 or 2, yellow or reddish, mitten-shaped to ellipsoid, 2.5–3 mm, smooth.

1 or 2, gray-brown, black-mottled, subglobose, 2.5 mm, smooth.

2n

= 32, 48.

Trifolium macrocephalum

Trifolium piorkowskii

Phenology Flowering Apr–Jun. Flowering Apr–May.
Habitat Rocky places, hard, compacted clay-gumbo, lava beds, sage-covered slopes, full sun. Shallow, vernally wet depres­sions on volcanic flats, banks of watercourses flowing through open rocky grassland, transitional habitats with scattered chaparral and conifers.
Elevation 80–2500 m. [260–8200 ft.] 300–800 m. [1000–2600 ft.]
Distribution
from FNA
CA; ID; NV; OR; WA
[WildflowerSearch map]
[BONAP county map]
from FNA
CA
Discussion

Trifolium macrocephalum has the largest inflorescences of any clover. Trifolium megacephalum Nuttall (1818) is an illegitimate replacement name for Lupinaster macrocephalum Pursh.

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

Trifolium piorkowskii is known only from Shasta County.

(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. 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. 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 Lupinaster macrocephalum
Name authority (Pursh) Poiret in J. Lamarck et al.: Encycl., suppl. 5: 336. (1817) Rand. Morgan & A. L. Barber: Novon, 23: 65, plate 1. (2014)
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