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   The Chenopodium genus, named by Linnaeus in 1753, "is difficult taxonomically" (Intermountain Flora). Species are best separated based on the characteristics of the fruit and pericarp (the fruit wall), and whether the pericarp is free from the seed or adheres to it. When the plants are not in fruit, then the important characteristics become the leaf shape, texture, and venation, and the height of plants. However, even when all morphological characteristics are present, getting to the identity of the species is problematic because of hybridization. Flora keys commonly do not agree about which characteristics belong to which species.

   I think that the best key to use is by Clemants and Mosyakin in the Flora of North America. You can scroll down through the key to find each of the species shown below and read the detailed descriptions and see drawings and range maps.

   Greek gives us both "chen" for a goose and "pous" for a foot.

Chenopodium album

Chenopodium album

Chenopodium album

Chenopodium album variety album (Lamb's Quarters)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, disturbed areas. Summer, fall.
Above and left: Near Yellow Jacket Canyon, September 15, 2020.

Chenopodium album grows to over two meters tall, but the plants shown here, growing in the drought of 2019-2020, are just 1/2 meter tall.

Some floras indicate that this is a native species in Colorado, but BONAP, the authority for this website, indicates that of the approximately 4 varieties of C. album (there is disagreement on the names and numbers of the varieties), only C. album variety missouriense is native to North America and in our area that variety is native only to New Mexico. It is adventive in just one or two counties in Colorado, Utah, and Arizona. 

Linnaeus named this species in 1753. "Album" means "white".

Click to read the detailed description of C. album in the Flora of North America. In that description, the following information is key to understanding C. album:

Chenopodium album, one of the worst weeds and most widespread synanthropic plants on the Earth, in its broad circumscription is also among the most polymorphic plant species. It is a loosely arranged aggregate of still insufficiently understood races. Hundreds of segregate microspecies and infraspecific entities (including nomenclatural combinations) of the C. album aggregate have been described and/or recognized by various authors. Some authors have recognized numerous segregate intergrading species, while others have developed elaborate infraspecific hierarchies with numerous subspecies, varieties, forms, and even numerous subforms (e.g., B. Jüttersonke and K. Arlt 1989), or have combined both approaches. Neither approach has brought satisfactory and uncontroversial results.

It is evident that most recent evolutionary processes within the group were greatly affected by anthropic factors, including extensive recent invasions, hybridization between previously geographically isolated taxa, poly-ploidy, intensive selective processes and mutagenesis in synanthropic habitats, gene drift, and so forth. All of these modern factors further complicated the taxonomic situation. Consequently, no infraspecific taxa are formally recognized in the present treatment. We attempt, however, to outline below the most common or noteworthy groups currently placed in Chenopodium album sensu lato. Although we list such groups under binomials, they should be considered here as informal groupings rather than accepted species.                   

Chenopodium album

Chenopodium album variety album (Lamb's Quarters)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, disturbed areas. Summer, fall.
Near Yellow Jacket Canyon, September 15, 2020.

Glomerules (densely packed flowers) give way to densely packed 5-ridged fruits, each with one, black seed which is very similar to the seed shown below for C. pratericola.

Chenopodium album

Chenopodium album

Chenopodium album variety album (Lamb's Quarters)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, disturbed areas. Summer, fall.
Near Yellow Jacket Canyon, September 15, 2020.

Upper surface of C. album leaves are reatively smooth and somewhat glaucous. Lower surface is farinose, i.e., with a mealy powdery covering, typical of many species of Chenopodium.

 

Chenopodium atrovirens (Pinyon Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, wet areas, disturbed areas. Summer.
Lizard Head Trail, August 22, 2007.

Chenopodium atrovirens grows from just two inches to two feet tall.  Flowers (not shown here) are 1/16 inch minute but are numerous in tight clusters (glomerules).  The flattened spherical fruit is enclosed in five sepals (red in the photograph at left), each of which is keeled and often dotted with microscopic white-to-pink grains.  These grains are shown below in a microscope photograph of the tip of one sepal.

Linnaeus named this genus in 1753 and Per Axel Rydberg named this species in 1900. "Atrovirens" means "dark green".

Click to read the detailed description of C. atrovirens in the Flora of North America.

Chenopodium atrovirens (Pinyon Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, wet areas, disturbed areas. Summer.
Lizard Head Trail, August 22, 2007.

Chenopodium atrovirens (Pinyon Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Foothills, montane. Openings, wet areas, disturbed areas. Summer.
Lower Stoner Mesa Trail, September 5, 2007.

Some seed pods have emptied and the star-shaped, symmetrical, tan and red pod is left behind.

 

Chenopodium pratericola

Chenopodium pratericola

Chenopodium pratericola
Chenopodium pratericola. Synonyms: Chenopodium desiccatum, Chenopodium leptophyllum. (Desert Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Semi-desert, foothills. Openings, disturbed areas. Summer, fall.
Above and left: Near Yellow Jacket Canyon, August 2, 2020.

Chenopodium pratericola grows to over three feet tall, often branching widely, as shown in the two photographs above. At left, a young plant is about 14 inches tall and one branch on the lower left side is several inches long.

No key that I used gave all the characteristics of the plants shown in this grouping, so I arrived at a species name based on the majority of characteristics that fit these plants. Most keys indicate that the structure of the seeds is a distinguishing characteristics. The seeds of the plants shown are smooth and black and easily separate from the seed chamber (the pericarp). But this seed description (coupled with a few other characteristics) best fits Chenopodium album. The leaf shape and texture of the leaves of the plants shown here do not, however, fit the description of those characteristics of C. album. C. pratericola is, I think, the best fit for these plants. See my note at the top of this page.

Even the common name gives us trouble, for a number of different species of Chenopodium are called "Lamb's Quarters". For many years I used that common name for the plants shown at left, but "Lamb's Quarters" is most often used for either C. album or C. berlandieri

Linnaeus named this genus in 1753 and Per Axel Rydberg named this species in 1912 from a collection made by J. B. Norton in Kansas in 1895. "Pratericola" is Latin for "meadow dwelling".

Click to read the detailed description of C. pratericola in the Flora of North America.

Chenopodium pratericola

Chenopodium pratericola. Synonyms: Chenopodium desiccatum, Chenopodium leptophyllum. (Desert Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Semi-desert, foothills. Openings, disturbed areas. Summer, fall.
Near Yellow Jacket Canyon, August 2, 2020.

Flowers are minute, petals are absent, and sepals are 1 mm or less wide and long.

Chenopodium pratericola

Chenopodium pratericola. Synonyms: Chenopodium desiccatum, Chenopodium leptophyllum. (Desert Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Semi-desert, foothills. Openings, disturbed areas. Summer, fall.
Near Yellow Jacket Canyon, September 14, 2020.

Each 3 mm by 3 mm triangular swollen pocket (made up of the sepals) contains a 1 mm wide smooth black seed which is closely encased in a microscopically thin pericarp that easily separates from the seed.

                             Chenopodium pratericola

Chenopodium pratericola

Chenopodium pratericola. Synonyms: Chenopodium desiccatum, Chenopodium leptophyllum. (Desert Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Semi-desert, foothills. Openings, disturbed areas. Summer fall.
Near Yellow Jacket Canyon, August 2, 2020.

Much of the plant is farinose, i.e., covered with what is defined as "a mealy, powdery coating". A microscopic examination shows that what appears white on the plant in these photos is a coating of very small, very thin, almost translucent but highly light reflective, cup-like, plastic-appearing structures. In a very thin layer, these overlay a green, gelatinous surface. The species of the genus Atriplex are also coated with a farinose layer, often sparkling red.

 

Chenopodium pratericola

Chenopodium pratericola. Synonyms: Chenopodium desiccatum, Chenopodium leptophyllum. (Desert Goosefoot)
Amaranthaceae (Amaranth),
formerly Chenopodiaceae (Goosefoot Family)

Semi-desert, foothills. Openings, disturbed areas. Summer fall.
Near Yellow Jacket Canyon, August 2, 2020.

Although leaf shape is variable, most leaves are linear to narrowly lanceolate. Lower stem leaves are occasionally triangular and toothed.

Range map © John Kartesz,
Floristic Synthesis of North America

State Color Key

Species present in state and native
Species present in state and exotic
Species not present in state

County Color Key

Species present and not rare
Species present and rare
Species extirpated (historic)
Species extinct
Species noxious
Species exotic and present
Native species, but adventive in state
Eradicated
Questionable presence

Chenopodium album variety album

Range map for Chenopodium album variety album

Range map for Chenopodium atrovirens

Chenopodium pratericola

Range map for Chenopodium pratericola