POLYGONACEAE

BUCKWHEAT FAMILY

James C. Hickman

Annual to trees, some dioecious
Stem: nodes often swollen
Leaves simple, basal or cauline, alternate, opposite, or whorled, generally entire; stipules 0 or obvious and fused into a generally scarious sheath around stem
Inflorescence: small cluster, axillary or arrayed in cymes or panicles; involucres sometimes subtending 1–many flowers
Flower generally bisexual, small, ± radial; perianth generally 5–6-lobed, base ± tapered, often jointed to pedicel; stamens 2–9, often in 2 whorls; ovary superior, styles generally 3, generally fused at base
Fruit: achene, generally enclosed by persistent perianth, generally 3-angled, ovoid, and glabrous
Genera in family: 50 genera, 1100 species: worldwide, especially n temp; some cultivated for food (Fagopyrum ; Rheum , rhubarb; Rumex , sorrel) or ornamental (Antigonon , coral-vine; Muehlenbeckia ; Polygonum )
Reference: [Ronse Decraene & Akeroyd 1988 Bot J Linn Soc 98:321–371; Reveal et al. 1989 Phytologia 66(2–4):83–414]
Treatments of the 15 eriogonoid genera are based on the monographic work of James L. Reveal, who is gratefully acknowledged.

ERIOGONUM

WILD BUCKWHEAT

Annual to shrub
Leaves generally ± basal (clustered on low stems or cauline), petioled, generally ± tomentose below (often shedding above); stipule 0
Inflorescence openly cyme-like, umbel-like, or head-like, generally ± scapose; bracts (any whorled, leaf-like structures on inflorescence) 3–many per node, leaf-like to scale-like; involucres generally 1 per node, generally ± obconic, lobes (or short teeth) generally 3–10, generally erect; flowers generally many per involucre, pedicelled
Flower: perianth white, yellow, or red, lobes 6, generally ± oblong to obovate; stamens 9
Fruit brown to black, glabrous to hairy
Species in genus: ± 250 species: North America
Etymology: (Greek: woolly knees, from hairy nodes of some)
Reference: [Reveal 1989 Phytologia 66:295–414]
Largest dicot genus in CA; apparently currently differentiating; many taxa ± indistinct. Better habitat data needed. Many are excellent bee fodder
Horticultural information: Most are attractive and easy to grow with good drainage.

Native

E. nudum Benth.

[Group 4] Perennial, 10–200 cm
Leaves basal or ± spaced on lower stem; blade 10–70 mm, oblanceolate to ovate, generally tomentose (especially below)
Inflorescence cyme- to head-like; axes glabrous, sometime wider below major nodes; bracts scale-like (lowest sometimes leaf-like); involucres 1–10 per cluster, 2–5 mm, teeth 5–8
Flower: perianth 1.5–4 mm, white, yellow, or red, subglabrous, stalk-like base 0
Fruit 1.5–3.5 mm, glabrous
Ecology: Abundant. Dry open places
Elevation: < 3800 m.
Bioregional distribution: California (except San Joaquin Valley, South Coast, Channel Islands, Modoc Plateau, Sonoran Desert)
Distribution outside California: to Washington, Nevada, nw Mexico
Varieties difficult, intergrading.

Native

var. pubiflorum Benth.

Leaves basal, 10–40 mm, becoming ± glabrous above; margins flat
Inflorescence slender, glabrous; involucres 3–10 per node, 2–5 mm, generally glabrous
Flower: perianth 2.5–3 mm, white or pale yellow, obviously hairy
Chromosomes: n=20
Ecology: Common. Dry flats, slopes
Elevation: 50–2000 m.
Bioregional distribution: Northwestern California, Cascade Range, Sierra Nevada, Sacramento Valley, San Francisco Bay Area, Mojave Desert
Distribution outside California: s Oregon, w Nevada
Intergrades with vars. oblongifolium & westonii
Horticultural information: SUN, DRN: 1, 2, 4, 5, 6, 7, 14, 15, 16, 17, 24.