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Epilobium minutum; photograph author not stated, no rights reserved CC0author not stated, no rights reserved · observed growing wild · 2026-05-31

Epilobium minutum Lindl. ex Lehm.

Small-flowered willowherb; Desert willowherb; Little willowherb; Minute willowherb

Onagraceae · British Columbia, Idaho +5

Cited as Kew's World Checklist cites it, Epilobium minutum Lindl. ex Lehm.: GBIF's backbone key for this page carries the name with another author, Lindl.

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Epilobium minutum, photograph (c) Parker James Lloyd, some rights reserved (CC BY)Epilobium minutum, photograph (c) Parker James Lloyd, some rights reserved (CC BY)Epilobium minutum, photograph author not stated, no rights reservedEpilobium minutum, photograph author not stated, no rights reservedEpilobium minutum, photograph (c) LJ Moore-McClelland, some rights reserved (CC BY)Epilobium minutum, photograph (c) LJ Moore-McClelland, some rights reserved (CC BY) 74 photographs ›
Habitat figures
Cold floor (1 night in 100)
-4.8°C
Record low -17.2 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
26°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,251mm
10 months of 25 mm or more in the median year CHELSA
Open-sky light
10–50DLI
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 November to March, with nights below freezing; no growing season read. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Epilobium minutum is a species of flowering plant, known by the common names little willowherb, chaparral willowherb and desert willowherb, in the family Onagraceae. It is also called "smallflower willowherb" in reference to its relatively small size. However that name, in particular the British English variant "small-flowered willowherb", typically refers to Epilobium parviflorum.

Quoted from Wikipedia, "Epilobium minutum", CC BY-SA 4.0.

About the genus · Epilobium

Epilobium is a genus of flowering plants in the family Onagraceae, containing about 197 species. The genus has a worldwide distribution. It is most prevalent in the subarctic, temperate and subantarctic regions, whereas in the subtropics and tropics Epilobium species are restricted to the cool montane biomes, such as the New Guinea Highlands.

Quoted from Wikipedia, "Epilobium", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads a rainy season and no growing season: 70% of the median year's rain (904 mm of 1,243 mm) falls in November to March, the cooler part of the year, but the mean nightly low is below freezing in February, March and January, so the rule reads no growing season from it. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: May to September.

Rain

1,243 mm in the median year at the habitat, 904 mm of it November to March. Wettest month December at 216 mm, driest month July at 13 mm. Across the grid cells of the range the year's total runs 573 mm to 2,548 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,251 mm, is the year's rain at the top of the page; the 1,243 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: 10 to 50 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 6, the highest 90th-percentile month 53).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -4.8 °C, the absolute minimum -17.2 °C, 3,066 frost nights in 44 years, 69.7 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 35.5 °C. Monthly means: the coldest month's mean nightly low -0.8 °C in December (across the grid cells of the range -9.7 °C to 4.7 °C), the warmest month's mean daily high 25.9 °C in July and August (median year across the grid cells of the range, CHELSA). Cold floor: -4.8 °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: 51 to 63% 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 +68 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 Epilobium minutum through the yearWarmest months July and August, mean daily high 26 °C; coldest month December, mean nightly low -0.8 °C; 1,243 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°frost35.5° 99th-percentile day, NASA POWER-17.2° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400500mm rainDLI 10–50RH 51–63%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 637 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 °C7 / -2–138 / 0–1410 / 3–1713 / 7–1917 / 12–2421 / 16–2826 / 19–3226 / 20–3222 / 17–2916 / 10–239 / 2–176 / -3–13
Night °C-1 / -9–5-1 / -8–51 / -6–63 / -3–87 / 1–1110 / 5–1313 / 8–1613 / 8–1611 / 5–147 / 0–112 / -6–7-1 / -10–5
Rain mm204 / 81–394166 / 61–316141 / 60–29686 / 39–19366 / 26–12939 / 6–10313 / 1–5017 / 2–5032 / 8–8786 / 34–217177 / 65–396216 / 82–454
DLI11 / 7–1517 / 13–2126 / 20–3135 / 29–4042 / 36–4747 / 38–5250 / 41–5344 / 36–4834 / 27–3922 / 15–2813 / 8–1810 / 6–14
RH %63 / 57–6761 / 57–6460 / 56–6458 / 53–6357 / 49–6255 / 45–6251 / 42–6151 / 42–6153 / 44–6157 / 49–6362 / 54–6763 / 57–67
How this section is made
Each figure is the median across the 637 grid cells on land that hold in-range records (963 records in those cells; 5 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 954:1124 (42.275, -123.775). Over 44 years there: absolute minimum -17.2 °C, 1st-percentile night -4.8 °C, 99th-percentile day 35.5 °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 637 distinct grid cells holding 963 of the 968 in-range records (5 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 954:1124 (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 42.50_-123.750, lapse-corrected +68 m at 6.5 °C/km. Elevation: ETOPO 2022, 720 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.
NativeBritish Columbia, Idaho, Montana, Oregon, Washington, California, Nevada · 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 marker38.447, -122.493 · in the densest population, 1112 records (74% 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 1502 georeferenced records inside the native range; the climate across the range on the 963 of them in the land cells it reads, of 968 placed to within 10 km; the map shows only the 548 openly licensed ones, which alone would put the marker 763 km away. 18 records outside the WCVP native range not used. 534 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.
Other GBIF keysRecords also from GBIF's key 3189155 (Epilobium minutum Lindl. ex Lehm.): Kew's file holds it as Epilobium minutum Lindl. ex Lehm. (accepted); 900 records, from GBIF's search API on the day of the build.
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 1502 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Epilobium minutum, photograph 1did not loadEpilobium minutum, photograph 2did not loadEpilobium minutum, photograph 3did not loadEpilobium minutum, photograph 4did not loadEpilobium minutum, photograph 5did not loadEpilobium minutum, photograph 6did not load

Photographs: (c) Parker James Lloyd, some rights reserved (CC BY) (2); author not stated, no rights reserved · CC0 (2); (c) LJ Moore-McClelland, 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.

Eriophyllum lanatum Eriophyllum lanatum Common woolly sunflower Photo: CC BY, Rosie YacoubCornus nuttallii Cornus nuttallii Pacific Dogwood Photo: CC BY, Alan RockefellerProsartes hookeri Prosartes hookeri Drops-of-gold Photo: CC BY, StarStatsMelica subulata Melica subulata Alaska oniongrass Photo: CC BY, humonGeranium oreganum Geranium oreganum Oregon geranium Photo: CC BY, Dee Shea HimesCollomia heterophylla Collomia heterophylla Variable-leaved collomia Photo: CC BY, Cody Hinchliff

Other Epilobium 37 in the reference

Epilobium alpestre Epilobium alpestre Whorled-leaved Willowherb Photo: CC BY, Johannes S.Epilobium alsinifolium Epilobium alsinifolium Chickweed Willowherb Photo: CC BY, Antoine ThivolleEpilobium anagallidifolium Epilobium anagallidifolium Alpine willowherb Photo: CC0, author not statedEpilobium billardiereanum Epilobium billardiereanum Robust willowherb Photo: CC BY, Arnim LittekEpilobium brachycarpum Epilobium brachycarpum Tall annual willowherb Photo: CC BY-SA, Josep GestiEpilobium brunnescens Epilobium brunnescens New Zealand Willowherb Photo: CC BY, James CunninghamEpilobium canum Epilobium canum Hummingbird trumpet Photo: CC BY, Grant ChovilEpilobium ciliatum Epilobium ciliatum American willowherb Photo: CC BY-SA, psweetEpilobium colchicum Epilobium colchicum Onagraceae Photo: CC BY, Алина УрусоваEpilobium coloratum Epilobium coloratum Cinnamon willowherb Photo: CC BY, Jeff ClarkEpilobium crassum Epilobium crassum Onagraceae Photo: CC0, author not statedEpilobium densiflorum Epilobium densiflorum Dense-flowered willowherb Photo: CC BY, gretchenparadis all 38 ›

Names & registers

Also known as Crossostigma lindleyi; Epilobium flexuosum; Epilobium lindleyi; Epilobium minutum var. canescens; Epilobium minutum var. minutum. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Onagraceae
Described by
Lindl. ex Lehm.
Native to
British Columbia, Idaho, Montana +4
Wild records
1502 in range · 548 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 2026-10-22GBIF's key 7644248 is Epilobium minutum Lindl.; the page links Kew's Epilobium minutum Lindl. ex Lehm., and the name is cited as Kew cites it
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 answeredasked 2026-10-22GBIF occurrence download https://doi.org/10.15468/dl.hbdw64, of 2026-10-21; 900 records of GBIF's key 3189155, Epilobium minutum Lindl. ex Lehm. (Kew's file holds it as Epilobium minutum Lindl. ex Lehm. (accepted)): GBIF occurrence search API; 12 records within 1 km of a botanic garden, herbarium or zoo left out (10 at a botanic garden or arboretum, 2 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 42.50_-123.750, lapse-corrected +68 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22found by its label; its IPNI identifier 92570-2 is Kew's for Epilobium minutum Lindl. ex Lehm.
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 66 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…