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Hordeum pusillum; photograph (c) Ryan Sorrells, some rights reserved (CC BY) CC BY(c) Ryan Sorrells, some rights reserved (CC BY) · observed growing wild · 2026-06-24

Hordeum pusillum Nutt.

Little barley; Little wild barley

Poaceae · Alberta, British Columbia +52

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Hordeum pusillum, photograph author not stated, no rights reservedHordeum pusillum, photograph author not stated, no rights reservedHordeum pusillum, photograph (c) Alexandria Szakacs, some rights reserved (CC BY)Hordeum pusillum, photograph (c) Alexandria Szakacs, some rights reserved (CC BY)Hordeum pusillum, photograph (c) Greghig Jirheg, some rights reserved (CC BY)Hordeum pusillum, photograph author not stated, no rights reserved 65 photographs ›
Habitat figures
Cold floor (1 night in 100)
-6.9°C
Record low -17.4 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
33°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
930mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
17–43DLI
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.

Summary

Hordeum pusillum, also known as little barley, is an annual grass native to most of the United States and southwestern Canada. It arrived via multiple long-distance dispersals of a southern South American species of Hordeum about one million years ago. Its closest relatives are therefore not the other North American taxa like meadow barley (Hordeum brachyantherum) or foxtail barley (Hordeum jubatum), but rather Hordeum species of the Pampas of central Argentina and Uruguay. It is less closely related to the Old World domesticated barley, from which it diverged about 12 million years ago. More on Wikipedia ›

Quoted from Wikipedia, "Hordeum pusillum", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (683 mm of 919 mm) takes 8 months, March to July and September to November. Mean temperature moves 20.7 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to January and March to May.

Rain

919 mm in the median year at the habitat, 683 mm of it March to July and September to November. Wettest months (2 at 109 mm), driest month January at 53 mm. Across the grid cells of the range the year's total runs 430 mm to 1,297 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 930 mm, is the year's rain at the top of the page; the 919 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: 17 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 13, the highest 90th-percentile month 48).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -6.9 °C, the absolute minimum -17.4 °C, 1,954 frost nights in 44 years, 44.4 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 42.3 °C. Monthly means: the coldest month's mean nightly low 3.4 °C in January (across the grid cells of the range -5.1 °C to 7.7 °C), the warmest month's mean daily high 33.3 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: -6.9 °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: 55 to 58% 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 +3 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

Habitat months, northern hemisphere

Habitat climate of Hordeum pusillum through the yearWarmest months July and August, mean daily high 33 °C; coldest month January, mean nightly low 3.4 °C; 919 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°frost42.3° 99th-percentile day, NASA POWER-17.4° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 17–43RH 55–58%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 1010 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 °C14 / 5–1716 / 8–1920 / 13–2225 / 18–2628 / 22–3031 / 27–3333 / 30–3533 / 29–3530 / 25–3125 / 19–2719 / 12–2214 / 6–18
Night °C3 / -5–85 / -3–99 / 1–1213 / 6–1618 / 12–2022 / 16–2323 / 18–2523 / 18–2520 / 15–2215 / 9–179 / 2–134 / -4–9
Rain mm53 / 16–9760 / 18–9475 / 31–10973 / 31–108109 / 52–141109 / 50–13867 / 47–11662 / 48–11279 / 37–114100 / 32–12971 / 21–12061 / 21–104
DLI19 / 15–2123 / 21–2729 / 28–3536 / 34–4338 / 37–4641 / 40–4843 / 40–4740 / 37–4233 / 30–3626 / 23–2920 / 16–2217 / 13–19
RH %57 / 53–5957 / 52–5956 / 51–5955 / 49–5958 / 51–6158 / 52–6156 / 51–6155 / 52–6156 / 52–5956 / 52–5857 / 51–5958 / 53–59
How this section is made
Each figure is the median across the 1010 grid cells on land that hold in-range records (1297 records in those cells; 4 more cells hold records but no land by the elevation layer, so those records sit at sea and the cells are left out), 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 1142:1648 (32.875, -97.575). Over 44 years there: absolute minimum -17.4 °C, 1st-percentile night -6.9 °C, 99th-percentile day 42.3 °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 1010 distinct grid cells holding 1297 of the 1304 in-range records (4 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 1142:1648 (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 33.00_-97.500, lapse-corrected +3 m at 6.5 °C/km. Elevation: ETOPO 2022, 257 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.
NativeAlberta, British Columbia, Colorado, Idaho, Montana, Oregon, Washington, Wyoming, Illinois, Iowa, Kansas, Minnesota, Missouri, North Dakota, Nebraska, Oklahoma, South Dakota, Wisconsin, Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, 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 Northeast, Mexico Northwest, Bermuda, Argentina Northeast, Argentina South, Argentina Northwest · introduced: Japan, Korea · 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 marker32.756, -97.357 · in the densest population, 389 records (22% 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 1806 georeferenced records inside the native range; the climate across the range on the 1297 of them in the land cells it reads, of 1304 placed to within 10 km; the map shows only the 701 openly licensed ones, which alone would put the marker 27 km away. 21 records outside the WCVP native range not used. 502 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 of the 1806 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Hordeum pusillum, photograph 1did not loadHordeum pusillum, photograph 2did not loadHordeum pusillum, photograph 3did not loadHordeum pusillum, photograph 4did not loadHordeum pusillum, photograph 5did not loadHordeum pusillum, photograph 6did not load

Photographs: author not stated, no rights reserved · CC0 (3); (c) Alexandria Szakacs, some rights reserved (CC BY) (2); (c) Greghig Jirheg, some rights reserved (CC BY).

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

Bothriochloa torreyana Bothriochloa torreyana Silver bluestem Photo: CC BY, Rich SommerToxicoscordion nuttallii Toxicoscordion nuttallii Nuttall's death camas Photo: CC0, author not statedPrunus rivularis Prunus rivularis Creek plum Photo: CC BY, IDClaireAcalypha persimilis Acalypha persimilis Euphorbiaceae Photo: CC BY, Clay Argythamnia mercurialina Euphorbiaceae Solidago radula Solidago radula Western rough goldenrod Photo: CC BY, saltyhiker

Other Hordeum 8 in the reference

Hordeum brachyantherum Hordeum brachyantherum Meadow barley Photo: CC BY, Abby HydeHordeum brevisubulatum Hordeum brevisubulatum Poaceae Photo: CC0, author not statedHordeum bulbosum Hordeum bulbosum Bulbous barley Photo: CC0, author not statedHordeum jubatum Hordeum jubatum Foxtail barley Photo: CC BY, Johnathan CampbellHordeum marinum Hordeum marinum Sea barley Photo: CC BY, Jorge ÍñiguezHordeum murinum Hordeum murinum Wall barley Photo: CC BY, Vasco Henrique Oliveira FonsecaHordeum secalinum Hordeum secalinum Meadow barley Photo: CC BY-SA, Victor HengHordeum vulgare Hordeum vulgare Barley Photo: CC BY, spacegecko

Names & registers

Also known as Critesion pusillum; Hordeum pusillum subsp. pusillum; Hordeum pusillum var. pubens; Hordeum pusillum var. pusillum; Hordeum pusillum var. typicum and 1 more. (GBIF Backbone)

Kew accepts as species of their own Hordeum intercedens: older names in GBIF's record of this species that Kew's World Checklist accepts as other species. (WCVP, RBG Kew, file of 2026-06-04)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Poaceae
Described by
Nutt.
Native to
Alberta, British Columbia, Colorado +51
Wild records
1806 in range · 701 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 2026-10-22
GBIF species record gbif.species answeredasked 2026-10-22
GBIF synonyms gbif.synonyms answeredasked 2026-10-22
GBIF common names gbif.vernacular answeredasked 2026-10-22names fetched 2026-10-22
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; 40 records within 1 km of a botanic garden, herbarium or zoo left out (22 at a botanic garden or arboretum, 6 at a herbarium, 12 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-22
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-22NASA POWER (MERRA-2) daily 1981–2024, cell 33.00_-97.500, lapse-corrected +3 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22
Wikipedia wikipedia answeredasked 2026-10-22
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 2026-10-22
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 128 datasets via GBIF.org; each carries its own licence.

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