CHENOPODIACEAE (Goosefoot Family)

(Judd and Ferguson, 1999)

Plants annual or perennial herbs (often shrubs or small trees elsewhere), sometimes monoecious or dioecious, sometimes slightly to strongly succulent, often with a taproot, glabrous or hairy, sometimes mealy (with short, white, inflated hairs that collapse and appear lozenge-shaped with age or upon drying), often tinged with pink to purple. Stems usually with fine longitudinal angles, stripes, or ridges. Leaves alternate or occasionally some leaves opposite, sometimes reduced to inconspicuous scales, simple but sometimes lobed, the margins variously entire, toothed, or wavy. Stipules absent. Inflorescences axillary and/or terminal, spikes, spikelike racemes, or panicles, often reduced to axillary clusters or solitary axillary flowers. Flowers sessile or very short-stalked, usually with 1–3 small, herbaceous bracts (usually 1 outer bract and 2 inner, often smaller bracteoles), imperfect or more commonly perfect, hypogynous (perigynous in Beta). Calyx absent or more commonly of 1–5 sepals, these free or fused toward the base, usually green at flowering, persistent and sometimes becoming hardened or papery at fruiting. Petals absent. Stamens 1–5, absent or reduced to minute staminodes in pistillate flowers, the filaments sometimes fused toward the base, the anthers attached basally or more or less toward their midpoints, usually yellow. Pistil 1 per flower (absent in staminate flowers), the ovary superior (partly inferior in Beta), consisting of 2 or 3 fused carpels, with 1 locule, the placentation usually basal. Styles 1–3, often very short, sometimes fused toward the base, the stigmas 1–3 (4 or 5 in the cultivated Spinacia), slender or capitate, occasionally lobed. Ovule 1 per flower. Fruits achenelike or less commonly capsules, sometimes winged, sometimes beaked, indehiscent or more commonly with irregular or circumscissile dehiscence. Seed 1, often somewhat flattened and lens-shaped, circular in outline or nearly so (the embryo appearing curved or coiled but not always easily observed). About 100 genera, about 1,500 species, worldwide.

The Chenopodiaceae are here treated in the traditional sense as a family separate from the Amaranthaceae. However, a number of morphological and molecular phylogenetic studies (Manhart and Rettig, 1993; Rodman, 1990, 1993; Downey et al., 1997; see also Judd et al., 1999) have presented evidence to suggest that the family as thus circumscribed is paraphyletic; that is, that the genera of Amaranthaceae represent a specialized subgroup within the lineage of Chenopodiaceae rather than a separate sister clade. Because some of the conclusions of these papers are contradictory and a few relationships among genera are yet controversial (such as the placement of Spinacia L.), it seems premature to combine these families in a floristic treatment until more detailed studies can be completed. The morphological features that generally separate the Chenopodiaceae from Amaranthaceae include their stamens with free (vs. basally fused) filaments and herbaceous (vs. papery) perianth and bracts, but numerous exceptions exist.

The family is economically important primarily as a source of food plants, including beets and Swiss chard (Beta), spinach (Spinacia), and grains (Chenopodium). An extract prepared from beets sometimes is used as a food coloring, and the genus is also a source of processed sugar. The family contains a number of noxious weeds of crop fields and sometimes also native plant communities, particularly Russian thistle (Salsola) and the pigweeds (Chenopodium). Members of the Chenopodiaceae are nearly all wind-pollinated and have been cited as causing hay fever. Pollen grains of most Amaranthaceae and Chenopodiaceae are virtually indistinguishable morphologically, and the two families are usually lumped into a single pollen class in projects that monitor airborne spores and pollen for air quality and hay fever reports.

Species of Chenopodiaceae have a well-deserved reputation for being difficult to determine. Users are cautioned that in this family mature fruits are usually necessary for identification of genera and species.