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Amaranthus powellii; photograph (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY) CC BY(c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY) · observed growing wild · 2026-09-25

Amaranthus powellii S.Watson

Powell's amaranth; Powell's smooth amaranth; Polwell's Amaranth; Powell's pigweed

Amaranthaceae · Colorado, Arizona +10

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Amaranthus powellii, photograph (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY)Amaranthus powellii, photograph (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY)Amaranthus powellii, photograph (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY)Amaranthus powellii, photograph (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY)Amaranthus powellii, photograph (c) thomas_oswald, some rights reserved (CC BY)Amaranthus powellii, photograph (c) thomas_oswald, some rights reserved (CC BY) 117 photographs ›
Habitat figures
Coldest month, mean nightly low
0.6°C
Dec at the habitat, not a floor; extremes not used (the weather cell's ground is too far off) CHELSA
Warmest month, mean daily high
27°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
503mm
9 months of 25 mm or more in the median year CHELSA
Open-sky light
19–52DLI
Lowest to highest month (DLI) CHELSA
The year in your months, northern hemisphere
  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug
  9. Sep
  10. Oct
  11. Nov
  12. Dec
Wet winters: the rain comes December to April, August and October, read as a winter growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Amaranthus powellii is a species of amaranth known by the common names Powell's amaranth and green amaranth.

Quoted from Wikipedia, "Amaranthus powellii", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads a winter growing season: 70% of the median year's rain (281 mm of 389 mm) falls in December to April, August and October, cooler than the year (wet-season mean 10.3 °C against a yearly mean of 12.9 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: February, April and June to October.

Rain

389 mm in the median year at the habitat, 281 mm of it December to April, August and October. Wettest month February at 45 mm, driest month June at 11 mm. Across the grid cells of the range the year's total runs 242 mm to 692 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 503 mm, is the year's rain at the top of the page; the 389 mm here is the median year's, the twelve monthly medians added, which the rain rule reads. Habitat calendar, northern hemisphere; median year across the grid cells of the range, CHELSA.

Light

Open sky over the habitat: 19 to 52 mol/m²/day across the year (daily light integral, median year across the grid cells of the range, CHELSA; the lowest 10th-percentile month across the cells is 13, the highest 90th-percentile month 54).

Warmth and air
Temperature

Monthly means: the coldest month's mean nightly low 0.6 °C in December (across the grid cells of the range -9.0 °C to 9.4 °C), the warmest month's mean daily high 27.0 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: none read. The nearest figure is 0.6 °C, the coldest month's mean nightly low, December, in the median year (CHELSA); a month's mean of its nightly lows is warmer than the nights a floor is read from. The daily extremes were read at a weather cell whose ground is too far above or below the typical spot to correct for, and are not used.

Humidity

Relative humidity at the habitat: 49 to 55% across the year (monthly means, median year across the grid cells of the range, CHELSA). A figure about the air, saying nothing about how the plant takes water.

How this section is made

Each card states this species' habitat figures with their sources, and what two fixed rules read from them; nothing here says what the plant does, wants or tolerates. The rules · the terms.

Seasons. Read from the median year of CHELSA monthly rainfall and mean temperature across the grid cells of the range: the rain rule takes the smallest set of months carrying 70% of the rain and calls it winter when its mean is more than half a degree below the year's, summer when more than that above, and neither in between; the temperature rule, used only under 120 mm, names the cooler six months when they are at least a degree cooler than the other six. Months are shifted for the other hemisphere only where the temperature curve moves 4 °C or more and the habitat lies 10° or more from the equator. A reading of the curves, not an observation of the plant.

Rain. CHELSA monthly precipitation, median year across the grid cells of the range. The rain that falls where the species is recorded; nothing about how the plant takes water.

Light. CHELSA shortwave radiation at each envelope cell, a daily-mean flux taken to a daily total and converted at 2.07 mol of PAR per MJ. The sky over the habitat, measured; what reaches a plant under a rock, a shrub or a shade cloth is not.

Temperature. CHELSA monthly means, median year across the grid cells of the range. No cold floor is read without a daily extremes series; the coldest month's mean nightly low named in its sentence is not one. Not a measured survival limit for any plant in a pot.

Humidity. CHELSA relative humidity, median year across the grid cells of the range.

Climate across the habitat

Habitat months, northern hemisphere

Habitat climate of Amaranthus powellii through the yearWarmest months July and August, mean daily high 27 °C; coldest month December, mean nightly low 0.6 °C; 389 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA. Habitat months, northern hemisphere.-10°0°10°20°30°40°frost°C · day and nightcold quarter0255075100125150mm rainDLI 19–52RH 49–55%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 57 habitat cells, CHELSA cold quarter: the three months around the coldest month's mean nightly low DLI, mol/m²/dayRH %each on its own scale
Figures by month
JanFebMarAprMayJunJulAugSepOctNovDec
Day °C12 / 2–2013 / 3–2115 / 8–2419 / 13–2522 / 18–2726 / 22–3127 / 21–3327 / 22–3325 / 20–3020 / 16–2615 / 8–2111 / 2–20
Night °C1 / -9–91 / -8–92 / -4–104 / -1–118 / 4–1312 / 9–1515 / 10–1815 / 10–1812 / 8–178 / 3–154 / -4–121 / -9–9
Rain mm43 / 9–13845 / 10–13144 / 13–9029 / 15–5419 / 9–5411 / 2–8723 / 1–10043 / 1–10426 / 5–9034 / 16–5629 / 12–6943 / 6–98
DLI21 / 15–3326 / 21–3836 / 30–4345 / 40–4749 / 44–5152 / 41–5450 / 40–5345 / 39–4838 / 35–4031 / 26–3423 / 17–3319 / 13–31
RH %54 / 50–6254 / 50–6053 / 47–5951 / 43–5851 / 41–5849 / 37–6150 / 41–6152 / 42–6151 / 44–6252 / 45–6055 / 47–5954 / 49–61

The daily extremes were not used: the correction for elevation, +1142 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's. So no cold floor is read for this species, and the coldest month's mean nightly low is not taken as one. What that cell gave, so corrected, over 44 years: absolute minimum -13.2 °C, 1st-percentile night -7.3 °C.

How this section is made
Each figure is the median across the 57 grid cells holding the 58 in-range records, with the 10th–90th percentile span across those cells after the slash where it differs. A dash is a month one or more of those cells has no figure for in the grid (a variable CHELSA does not carry there), so no median is taken rather than one over fewer cells. Extremes and elevation were read at a typical spot in the range, cell 1159:1281 (32.025, -115.925). Normals: CHELSA V2.1 1981–2010 climatology, 0.05° cells (each the mean of ~36 1 km pixels). Across the range: median and 10th–90th percentile of each month across the 57 distinct grid cells holding 58 of the 58 in-range records; extremes and elevation at the typical cell 1159:1281 (its coldest month's mean nightly low nearest the median across cells); its position is the cell centre. Extremes: NASA POWER (MERRA-2) daily 1981–2024, cell 32.00_-115.625, lapse-corrected +1142 m at 6.5 °C/km. Elevation: ETOPO 2022, 1667 m (cell mean).

Natural habitat

Native range as published by WCVP; the marker is where the records are densest and decides nothing: the climate was read across the cells of the in-range records placed well enough to read one, not at the marker.
Openly licensed records inside the range, framed on where they fall.
NativeColorado, Arizona, California, Nevada, Utah, New Mexico, Texas, Mexico Central, Mexico Northeast, Mexico Northwest, Mexico Southwest, Mexico Southeast · introduced: Denmark, Finland, Great Britain, Norway, Sweden, Austria, Czechoslovakia, Germany, Hungary, France, Greece, Italy, Kriti, Baltic States, Central European Russia, South European Russia, Northwest European Russia, Ukraine, Algeria, Morocco, Canary Is., Ethiopia, Tanzania, Uganda, Irkutsk, Kazakhstan, North Caucasus, Transcaucasus, Cyprus, Manchuria, Korea, India, Pakistan, West Himalaya, New South Wales, Northern Territory, Queensland, South Australia, Tasmania, Victoria, Western Australia, New Zealand North, New Zealand South, Alberta, British Columbia, Saskatchewan, Ontario, Prince Edward I., Québec, Idaho, Montana, Oregon, Washington, Wyoming, Illinois, Iowa, Kansas, Minnesota, Missouri, Oklahoma, South Dakota, Wisconsin, Connecticut, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Alabama, Arkansas, Florida, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, Bolivia, Ecuador, Peru, Argentina Northwest, Chile Central · regions are the level-3 units of the World Geographical Scheme for Recording Plant Distributions, as Kew's World Checklist records ranges, some under historical names such as Yugoslavia or Czechoslovakia (how).
Map marker37.669, -117.908 · in the densest population, 56 records (46% of those in range)
Kew's description“annual” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 121 georeferenced records inside the native range; the climate across the range on the 58 of them placed to within 10 km; the map shows only the 54 openly licensed ones, which alone would put the marker 564 km away. 1511 records outside the WCVP native range not used. 63 in-range records are placed to worse than 10 km, or with no stated accuracy (admitted only as a person's observation to three decimals), and stay on the map but off the climate.
How this section is made
The map marker: the openly licensed record nearest the middle of the densest 1° population inside the densest 4° block of the 121 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Amaranthus powellii, photograph 1did not loadAmaranthus powellii, photograph 2did not loadAmaranthus powellii, photograph 3did not loadAmaranthus powellii, photograph 4did not loadAmaranthus powellii, photograph 5did not loadAmaranthus powellii, photograph 6did not load

Photographs: (c) Cosimo Costanzia di Costigliole, some rights reserved (CC BY) (4); (c) thomas_oswald, some rights reserved (CC BY) (2).

Similar habitat climate The 6 nearest by mean daily high, mean nightly low and rain, month by month. How.

Solidago velutina Solidago velutina Three-nerve goldenrod Photo: CC BY, Henrik KibakCarex senta Carex senta Swamp carex Photo: CC BY-SA, Vincent WeberCeanothus pauciflorus Ceanothus pauciflorus Mojave Desert Whitethorn Photo: CC BY, William HarmonEriogonum wrightii Eriogonum wrightii Bastard-sage Photo: CC BY, Jo RobertsArctostaphylos pringlei Arctostaphylos pringlei Pinkbracted manzanita Photo: CC BY, Matt BergerRhodanthemum gayanum Rhodanthemum gayanum Asteraceae Photo: CC BY, Joey Bom

Other Amaranthus 23 in the reference

Amaranthus albus Amaranthus albus White pigweed Photo: CC0, author not statedAmaranthus australis Amaranthus australis Southern amaranth Photo: CC0, author not statedAmaranthus blitoides Amaranthus blitoides Prostrate pigweed Photo: CC BY, Tatyana SovaAmaranthus blitum Amaranthus blitum Purple amaranth Photo: CC BY, Jason GrantAmaranthus caudatus Amaranthus caudatus Love-lies-bleeding Photo: CC BY, Evgenij SamarinAmaranthus cruentus Amaranthus cruentus Purple amaranth Photo: CC0, author not statedAmaranthus deflexus Amaranthus deflexus Perennial pigweed Photo: CC BY-SA, Pere BarnolaAmaranthus dubius Amaranthus dubius Spleen Amaranth Photo: CC BY, scallionsAmaranthus fimbriatus Amaranthus fimbriatus Amaranthaceae Photo: CC BY, Jo Roberts Amaranthus floridanus Florida amaranth Amaranthus graecizans Amaranthus graecizans Mediterranean amaranth Photo: CC BY, Michael AndresekAmaranthus hybridus Amaranthus hybridus Green amaranth Photo: CC BY, zebedeugalinha all 24 ›

Names & registers

Also known as Amaranthus bracteosus; Amaranthus chlorostachys subsp. pseudoretroflexus; Amaranthus chlorostachys var. powellii; Amaranthus chlorostachys var. pseudoretroflexus; Amaranthus hybridus f. pseudoretroflexus and 9 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Amaranthaceae
Described by
S.Watson
Native to
Colorado, Arizona, California +9
Wild records
121 in range · 54 open

Every figure here is derived from public data by a stated rule and names its source; nothing about this species is written for its page by a person or by AI, apart from the marked, credited quotations. How →

Where this page came from built 2026-10-21
GBIF species record gbif.species answeredasked 2026-10-21
GBIF synonyms gbif.synonyms answeredasked 2026-10-21
GBIF common names gbif.vernacular answeredasked 2026-10-21names fetched 2026-10-21
WCVP native range wcvp.distribution answeredas of 2026-06-04
GBIF occurrence records gbif.occurrences answeredas of 2026-10-21GBIF occurrence download https://doi.org/10.15468/dl.hbdw64, of 2026-10-21; 31 records within 1 km of a botanic garden, herbarium or zoo left out (22 at a botanic garden or arboretum, 3 at a herbarium, 6 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-21
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-21NASA POWER (MERRA-2) daily 1981–2024, cell 32.00_-115.625, lapse-corrected +1142 m at 6.5 °C/km; read, and set aside: the correction for elevation, +1142 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's, so no cold floor is shown
Wikidata wikidata answeredasked 2026-10-21
Wikipedia wikipedia answeredasked 2026-10-21
iNaturalist photographs, wild inat.photos.wild answeredasked 2026-10-22from iNaturalist's open data of 2026-09-27: research-grade observations with an open-licence photograph, the 24 whose photographs iNaturalist received last (the open data holds no votes); filled 2026-10-22
iNaturalist photographs, cultivated inat.photos.cultivated not asked
GBIF media gbif.media answeredasked 2026-10-21
OpenAlex papers openalex not askednot yet asked for this reference; a later fill takes the papers from OpenAlex's snapshot

Every source is recorded as having answered, reported nothing, refused, failed, not been asked, or answered twice where one answer is taken (“not taken: two items answered”), and, for a source asked when this page was built, when: the figures are as the source held them that day; a source read from a file (Kew's World Checklist, a GBIF download) says "as of" the file's day instead; a row carried from an earlier build of the page names that build instead. Only “nothing to report” is ever shown as an absence. Records came from 178 datasets via GBIF.org; each carries its own licence.

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