# Amaranthaceae
**Amaranthaceae** Juss. is a family of flowering plants in the order [Caryophyllales](https://www.edgepedia.org/caryophyllales), published in 1789 and conserved under that name[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). In its broad sense (sensu lato) it includes the former goosefoot family Chenopodiaceae, giving a cosmopolitan family of roughly 185 genera and 2,050 to 2,500 species[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). The narrow sense (sensu stricto) covers 65 to 79 genera with 800 to 900 species, and counts vary among authors[2](https://academic.oup.com/aob/article/137/3/609/8277962?login=false). The family includes crops such as amaranth, quinoa, spinach, and sugar beet, as well as ornamentals[3](https://bioone.org/journals/Willdenowia/volume-45/issue-3/wi.45.45301/A-taxonomic-backbone-for-the-global-synthesis-of-species-diversity/10.3372/wi.45.45301.pdf).
| Key fact | Detail |
|---|---|
| Name and rank | Amaranthaceae Juss., first published 1789, nom. cons.; accepted family in Caryophyllales[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) |
| Size | Broad sense: c. 185 genera, 2,050–2,500 species; narrow sense: 65–79 genera, 800–900 species[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) • [2](https://academic.oup.com/aob/article/137/3/609/8277962?login=false) |
| Distribution | Cosmopolitan; some species widespread in tropical, subtropical and temperate regions, others especially common in the Old World[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) |
| Flower structure | Small actinomorphic flowers with dry papery bracts; petals absent; tepals usually 3–5; stamens opposite the tepals; ovary superior with basal placentation[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) |
| Fruits and seeds | Capsules (mainly circumsessile), nuts, utricles or achenes, rarely berries; seeds black and shiny[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) |
| Ecology | Deserts, semi-deserts and saline areas; many drought- and salt-tolerant species[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) • [3](https://bioone.org/journals/Willdenowia/volume-45/issue-3/wi.45.45301/A-taxonomic-backbone-for-the-global-synthesis-of-species-diversity/10.3372/wi.45.45301.pdf) |
| Photosynthesis | 17 distinct C4 leaf types, most marking independent origins of C4 photosynthesis; the only angiosperm family with terrestrial C4 plants lacking Kranz anatomy[4](https://www.journals.uchicago.edu/doi/10.1086/378649) • [5](https://pmc.ncbi.nlm.nih.gov/articles/PMC3527620/) |
## Description
Most members are annual or perennial herbs, subshrubs or shrubs, rarely trees or lianas; stems are frequently angular, sometimes succulent, with swollen nodes, and stipules are absent[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). Leaves are simple, alternate or opposite, with entire or nearly entire margins, and are sometimes reduced or succulent[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information).
The flowers are small and mostly actinomorphic, bisexual or unisexual, with plants that may be dioecious, monoecious or polygamous[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). They are associated with dry, papery bracts and bracteoles and are densely clustered in cymose spikes, heads or panicles; lateral flowers of the small cymules are occasionally sterile and modified into scales, spines, bristles or hooked hairs[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). The perianth is uniseriate, membranous to firm, with tepals (0–)5(–8) that are free or fused and may persist and harden in fruit; petals are absent[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). Stamens are usually as many as and opposite the tepals, with filaments free or fused into a tube or cup, sometimes alternating with pseudostaminodes[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). The ovary is superior, unilocular, with one to many ovules on basal placentation[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information).
Fruits are capsules that dehisce irregularly or by a circumscissile lid, nuts, utricles or achenes, rarely berries, usually enclosed by the persistent perianth; seeds are globular, lenticular or ovoid, black and shiny, with a curved to circular embryo surrounding copious endosperm, and are dispersed by wind, water and animals[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information).
## Distribution and ecology
The family is cosmopolitan, with some species widespread across tropical, subtropical and temperate regions and others especially common in the [Old World](https://www.edgepedia.org/old-world)[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). Kew's temperate handbook notes that the family includes many drought- and salt-tolerant species and several widespread invasive weeds[3](https://bioone.org/journals/Willdenowia/volume-45/issue-3/wi.45.45301/A-taxonomic-backbone-for-the-global-synthesis-of-species-diversity/10.3372/wi.45.45301.pdf). Amaranthaceae sensu lato is recognized for its capacity to establish itself and flourish in harsh settings, including salty soils, dry habitats, and sites contaminated by heavy metals[6](https://onlinelibrary.wiley.com/doi/10.1111/cla.70049).
## Relationship with Chenopodiaceae
Amaranthaceae and Chenopodiaceae have long been regarded as closely related, and their separate family status was a subject of phylogenetic and taxonomic debate[7](https://doi.org/10.1093/sysbio%2Fsyaa066). Molecular studies using the markers rbcL and matK resolved the two as sister families, and the combined Amaranthaceae-Chenopodiaceae clade as sister to the Achatocarpaceae[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). On this evidence the Angiosperm Phylogeny Group's APG III classification of 2009 merged Chenopodiaceae into Amaranthaceae, a merger supported by morphological, anatomical, phytochemical and molecular lines of evidence[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information) • [6](https://onlinelibrary.wiley.com/doi/10.1111/cla.70049). A 2024 phylogenomic study confirmed that traditional Chenopodiaceae is monophyletic and that Amaranthaceae sensu stricto is its sister taxon, while attributing earlier inconsistent phylogenies to cytonuclear conflict, habitat-driven gene selection and incomplete lineage sorting[8](https://pmc.ncbi.nlm.nih.gov/articles/PMC11246835/).
## Photosynthesis
The family is a major center of C4 photosynthesis, a carbon-concentrating mechanism that suppresses photorespiration (wasteful oxygen-based plant reaction that C4 photosynthesis suppresses). A survey of C4 leaf anatomy in Amaranthaceae and Chenopodiaceae revealed 17 different leaf types, in most cases each marking an independent origin of C4 photosynthesis[4](https://www.journals.uchicago.edu/doi/10.1086/378649). Amaranthaceae sensu lato exceeds the grasses (Poaceae) and sedges ([Cyperaceae](https://www.edgepedia.org/cyperaceae)) in the diversity of its photosynthetic organ anatomy, and it is the only angiosperm family containing terrestrial C4 plants that lack Kranz anatomy, the dual-cell leaf structure typical of C4 plants; three species run a single-cell rather than dual-cell C4 system[5](https://pmc.ncbi.nlm.nih.gov/articles/PMC3527620/). C4 species of the family also show stronger osmotic adaptation and greater salt tolerance than their C3 relatives[9](https://pmc.ncbi.nlm.nih.gov/articles/PMC13074355/).
## Recent phylogenomics and classification
The evolutionary history of Amaranthaceae sensu stricto has been shaped by multiple whole-genome duplications and rapid radiations, which long left its internal relationships unresolved[10](https://pubmed.ncbi.nlm.nih.gov/42415398/). A phylogenomic study using a customized bait set targeting 1,000 low-copy nuclear loci reconstructed a globally sampled phylogeny representing 96 percent of all recognized genera, drawing on many rare and previously inaccessible taxa obtained largely from herbarium collections[10](https://pubmed.ncbi.nlm.nih.gov/42415398/).
The results revealed a strongly reticulate and highly polyploid history, involving at least two deep hybridization events and up to six ancient whole-genome duplications, which generated substantial gene tree discordance along the backbone of the phylogeny[10](https://pubmed.ncbi.nlm.nih.gov/42415398/). On this basis the study recognized 11 tribes within Amaranthaceae sensu stricto, including the newly described tribes Allmaniopseae and Wadithamneae, providing a framework intended to give long-term stability to the family's classification[10](https://pubmed.ncbi.nlm.nih.gov/42415398/).
## Notable genera
The type genus *Amaranthus* L. was first published in 1753 in Species Plantarum, is cosmopolitan in native range, and includes 93 accepted species, among them the grain amaranths *[Amaranthus caudatus](https://www.edgepedia.org/amaranthus-caudatus)*, *Amaranthus cruentus*, and *[Amaranthus hypochondriacus](https://www.edgepedia.org/amaranthus-hypochondriacus)* and widespread weeds such as *Amaranthus retroflexus* and *Amaranthus palmeri*[11](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A327362-2). Other genera listed for the family include *Alternanthera*, *[Celosia](https://www.edgepedia.org/celosia)*, *Gomphrena*, and *Iresine*, several of which are grown as ornamentals[1](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information). The broader family also supplies food crops such as quinoa, spinach, and sugar beet, formerly placed in Chenopodiaceae[3](https://bioone.org/journals/Willdenowia/volume-45/issue-3/wi.45.45301/A-taxonomic-backbone-for-the-global-synthesis-of-species-diversity/10.3372/wi.45.45301.pdf).
## References
1. [Amaranthaceae Juss., Plants of the World Online, Kew Science](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A30000566-2/general-information)
2. [Current state of our knowledge of the domestication and evolution of the grain amaranths: a critical standpoint, Annals of Botany](https://academic.oup.com/aob/article/137/3/609/8277962?login=false)
3. [A taxonomic backbone for the global synthesis of species diversity, Willdenowia](https://bioone.org/journals/Willdenowia/volume-45/issue-3/wi.45.45301/A-taxonomic-backbone-for-the-global-synthesis-of-species-diversity/10.3372/wi.45.45301.pdf)
4. [Kadereit et al., Phylogeny of Amaranthaceae and Chenopodiaceae and the Evolution of C4 Photosynthesis, International Journal of Plant Sciences](https://www.journals.uchicago.edu/doi/10.1086/378649)
5. [Rubisco Evolution in C4 Eudicots: An Analysis of Amaranthaceae Sensu Lato, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC3527620/)
6. [Evolutionary framework and tribal circumscription of Amaranthaceae sensu stricto based on a comprehensive phylogenomic analysis, Cladistics](https://onlinelibrary.wiley.com/doi/10.1111/cla.70049)
7. [Disentangling Sources of Gene Tree Discordance in Phylogenomic Data Sets: Testing Ancient Hybridizations in Amaranthaceae s.l., Systematic Biology](https://doi.org/10.1093/sysbio%2Fsyaa066)
8. [An updated phylogeny and adaptive evolution within Amaranthaceae s.l. inferred from multiple phylogenomic datasets, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC11246835/)
9. [Distinguished Features of Adaptive Strategies of Halophytes and Glycophytes with Different Types of Photosynthesis in Response to Climatic Stressors, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC13074355/)
10. [Evolutionary framework and tribal circumscription of Amaranthaceae sensu stricto based on a comprehensive phylogenomic analysis, PubMed](https://pubmed.ncbi.nlm.nih.gov/42415398/)
11. [Amaranthus L., Plants of the World Online, Kew Science](https://powo.science.kew.org/taxon/urn%3Alsid%3Aipni.org%3Anames%3A327362-2)
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*Topic: Encyclopedia › Life and health › Plants and algae › Seed plants › Other flowering plants*
*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license