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Amaranthus retroflexus; photograph (c) Oleksandr Shynder, some rights reserved (CC BY) CC BY(c) Oleksandr Shynder, some rights reserved (CC BY) · observed growing wild · 2026-09-23

Amaranthus retroflexus L.

Common amaranth; Redroot amaranth; Redroot pigweed; Rough pigweed

Amaranthaceae · Mexico Central, Mexico Northeast +3

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Amaranthus retroflexus, photograph (c) Oleksandr Shynder, some rights reserved (CC BY)Amaranthus retroflexus, photograph (c) Мирослав Соболев, some rights reserved (CC BY)Amaranthus retroflexus, photograph (c) Мирослав Соболев, some rights reserved (CC BY)Amaranthus retroflexus, photograph (c) Pere Barnola, some rights reserved (CC BY-SA)Amaranthus retroflexus, photograph (c) Codrin Bucur, some rights reserved (CC BY)Amaranthus retroflexus, photograph (c) Maria Kohanovskaya, some rights reserved (CC BY) 59 photographs ›
Habitat figuresfrom few records
Cold floor (1 night in 100)
-3.5°C
Record low -13.4 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
35°C
Aug at the habitat CHELSA
Rain a year (median across the range)
828mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
18–43DLI
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
Rain spread: 70% of the median year's rain takes 8 months, so no short rainy season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

From few records: 6 records in 5 grid cells. The records.

Summary

Amaranthus retroflexus is a species of flowering plant in the family Amaranthaceae with several common names, including red-root amaranth, redroot pigweed, red-rooted pigweed, common amaranth, pigweed amaranth, and common tumbleweed.

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

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (620 mm of 821 mm) takes 8 months, March to October. Mean temperature moves 18.1 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to April.

Rain

821 mm in the median year at the habitat, 620 mm of it March to October. Wettest month June at 113 mm, driest months (2 at 48 mm). Across the grid cells of the range the year's total runs 801 mm to 850 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 828 mm, is the year's rain at the top of the page; the 821 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: 18 to 43 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 18, the highest 90th-percentile month 46).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -3.5 °C, the absolute minimum -13.4 °C, 604 frost nights in 44 years, 13.7 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 40.9 °C. Monthly means: the coldest month's mean nightly low 7.0 °C in January (across the grid cells of the range 6.1 °C to 12.0 °C), the warmest month's mean daily high 34.6 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: -3.5 °C, which is the 1st-percentile night over 44 years at a typical spot in the range (NASA POWER).

Humidity

Relative humidity at the habitat: 56 to 60% 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. NASA POWER daily minima and maxima over 44 years at a typical spot in the range, lapse-corrected +11 m to its elevation; CHELSA monthly means, median year across the grid cells of the range. The cold floor is the 1st-percentile night named in its sentence. 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

From few records: this habitat climate is read from 6 records in 5 grid cells; a page says so under 12 records or 5 cells, and shows the figures as read.

Habitat months, northern hemisphere

Habitat climate of Amaranthus retroflexus through the yearWarmest month August, mean daily high 35 °C; coldest month January, mean nightly low 7.0 °C; 821 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA; the extremes at the edge from NASA POWER. Habitat months, northern hemisphere.-20°-10°0°10°20°30°40°50°frost40.9° 99th-percentile day, NASA POWER-13.4° lowest night in 44 years, NASA POWER°C · day and nightcold quarter050100150200mm rainDLI 18–43RH 56–60%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 5 habitat cells, CHELSA cold quarter: the three months around the coldest month's mean nightly low extremes over 44 years at a typical spot in the range, from NASA POWER, marked at the edge, in no month DLI, mol/m²/dayRH %each on its own scale
Figures by month
JanFebMarAprMayJunJulAugSepOctNovDec
Day °C18 / 17–2620 / 20–2723 / 23–3027 / 25–3330 / 26–3333 / 26–3334 / 25–3435 / 25–3532 / 24–3227 / 23–2922 / 21–2718 / 18–26
Night °C7 / 6–129 / 7–1312 / 9–1616 / 12–1920 / 14–2123 / 16–2324 / 15–2424 / 15–2422 / 15–2217 / 13–1912 / 9–158 / 7–13
Rain mm48 / 9–4948 / 7–4959 / 7–6061 / 15–6290 / 51–94113 / 111–16768 / 66–17355 / 51–16879 / 76–15995 / 59–10255 / 10–5950 / 4–52
DLI19 / 19–3423 / 23–3929 / 29–4435 / 35–4637 / 37–4541 / 40–4243 / 41–4341 / 39–4234 / 34–3727 / 27–3520 / 20–3418 / 18–32
RH %57 / 49–5857 / 47–5857 / 45–5757 / 46–5760 / 49–6059 / 56–6058 / 56–6056 / 56–6057 / 57–6158 / 56–5958 / 52–5857 / 50–58
How this section is made
Each figure is the median across the 5 grid cells holding the 6 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 1210:1633 (29.475, -98.325). Over 44 years there: absolute minimum -13.4 °C, 1st-percentile night -3.5 °C, 99th-percentile day 40.9 °C. 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 5 distinct grid cells holding 6 of the 6 in-range records; extremes and elevation at the typical cell 1210:1633 (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 29.50_-98.125, lapse-corrected +11 m at 6.5 °C/km. Elevation: ETOPO 2022, 211 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.
No openly licensed record to show inside the range.
NativeMexico Central, Mexico Northeast, Mexico Gulf, Mexico Southwest, Mexico Southeast · introduced: Denmark, Finland, Great Britain, Ireland, Norway, Sweden, Austria, Belgium, Czechoslovakia, Germany, Hungary, Netherlands, Poland, Switzerland, Baleares, Corse, France, Portugal, Sardegna, Spain, Albania, Bulgaria, Greece, Italy, Romania, Sicilia, Turkey-in-Europe, Yugoslavia, Belarus, Baltic States, Krym, Central European Russia, East European Russia, South European Russia, Northwest European Russia, Ukraine, Algeria, Egypt, Libya, Morocco, Tunisia, Azores, Canary Is., Madeira, Burkina, Mauritania, Chad, Zambia, Zimbabwe, KwaZulu-Natal, Altay, Irkutsk, Krasnoyarsk, Tuva, West Siberia, Yakutskiya, Amur, Khabarovsk, Magadan, Primorye, Sakhalin, Kazakhstan, Kirgizistan, Turkmenistan, Tadzhikistan, Uzbekistan, North Caucasus, Transcaucasus, Afghanistan, Cyprus, East Aegean Is., Iran, Iraq, Lebanon-Syria, Palestine, Sinai, Turkey, Gulf States, Inner Mongolia, Manchuria, China North-Central, China Southeast, Xinjiang, Mongolia, Japan, Korea, Nansei-shoto, India, Pakistan, West Himalaya, Cambodia, Vietnam, New South Wales, South Australia, Victoria, Western Australia, New Zealand North, New Zealand South, Nunavut, Northwest Territories, Alberta, British Columbia, Manitoba, Saskatchewan, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward I., Québec, Colorado, Idaho, Montana, Oregon, Washington, Wyoming, Illinois, Kansas, Minnesota, Missouri, North Dakota, Nebraska, Oklahoma, South Dakota, Wisconsin, Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Arizona, California, Nevada, Utah, New Mexico, Texas, Alabama, Arkansas, Delaware, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, District of Columbia, Mexico Northwest, Trinidad-Tobago, Venezuela, Bolivia, Brazil West-Central, Brazil Northeast, Brazil Southeast, Brazil South, Argentina Northeast, Argentina South, Chile Central, Chile North, Paraguay, Uruguay · 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 marker29.45, -98.45 · in the densest population, 4 records (67% 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 and the climate across the range rest on all 6 georeferenced records inside the native range; none carries a licence permitting republication, so the map shows no points. 755 records outside the WCVP native range not used. Under a dozen records behind the map and the climate.
How this section is made
The map marker: the centre of the tenth-degree cell nearest the middle (no openly licensed record lies in the population, so no record's coordinates are published) of the densest 1° population of the 6 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 retroflexus, photograph 1did not loadAmaranthus retroflexus, photograph 2did not loadAmaranthus retroflexus, photograph 3did not loadAmaranthus retroflexus, photograph 4did not loadAmaranthus retroflexus, photograph 5did not loadAmaranthus retroflexus, photograph 6did not load

Photographs: (c) Oleksandr Shynder, some rights reserved (CC BY); (c) Мирослав Соболев, some rights reserved (CC BY) (2); (c) Pere Barnola, some rights reserved (CC BY-SA); (c) Codrin Bucur, some rights reserved (CC BY); (c) Maria Kohanovskaya, some rights reserved (CC BY).

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

Fraxinus berlandieriana Fraxinus berlandieriana Berlandier ash Photo: CC BY, Craig HensleyAristolochia erecta Aristolochia erecta Dutchman's pipe Photo: CC BY, Cleveland PowellAmaranthus polygonoides Amaranthus polygonoides Tropical amaranth Photo: CC BY, Linda Jo ConnSolanum triquetrum Solanum triquetrum Texas nightshade Photo: CC BY-SA, Turner BrockmanMetastelma barbigerum Metastelma barbigerum Apocynaceae Photo: CC BY, RachelRuellia ciliatiflora Ruellia ciliatiflora Hairyflower wild petunia Photo: CC BY, Reanne ("Bean") Dunn

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 bulgaricus; Amaranthus bullatus; Amaranthus chlorostachys; Amaranthus curvifolius; Amaranthus delilei and 20 more. (GBIF Backbone)

Under another author Amaranthus dubius E.H.L.Krause is an older name of this species, not Amaranthus dubius, a species of the reference. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Amaranthaceae
Described by
L.
Native to
Mexico Central, Mexico Northeast, Mexico Gulf +2
Wild records
6 in range · 0 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 answeredasked 2026-10-21GBIF occurrence search API; 21 records within 1 km of a botanic garden, herbarium or zoo left out (17 at a botanic garden or arboretum, 4 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 29.50_-98.125, lapse-corrected +11 m at 6.5 °C/km
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 7 datasets via GBIF.org; each carries its own licence.

Cultifolio

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