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Acanthus montanus; photograph (c) Philippe Hornus, some rights reserved (CC BY) CC BY(c) Philippe Hornus, some rights reserved (CC BY) · observed growing wild · 2011-07-31

Acanthus montanus (Nees) T.Anderson

Mountain thistle; Bear's breech

Acanthaceae · Benin, Nigeria +12

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Acanthus montanus, photograph (c) Philippe Hornus, some rights reserved (CC BY)Acanthus montanus, photograph (c) Philippe Hornus, some rights reserved (CC BY)Acanthus montanus, photograph author not stated, no rights reservedAcanthus montanus, photograph author not stated, no rights reservedAcanthus montanus, photograph author not stated, no rights reservedAcanthus montanus, photograph author not stated, no rights reserved 25 photographs ›
Habitat figures
Cold floor (1 night in 100)
19.9°C
Record low 14.9 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
32°C
Feb at the habitat CHELSA
Rain a year (median across the range)
2,569mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
23–34DLI
Lowest to highest month (DLI) CHELSA
The year in the habitat's months, not shifted
  1. Jan
  2. Feb
  3. Mar
  4. Apr
  5. May
  6. Jun
  7. Jul
  8. Aug
  9. Sep
  10. Oct
  11. Nov
  12. Dec
A sharp rainy season, May to October (the habitat's months, not shifted), in a year of even temperature. rain rule, CHELSA
Not shifted: the shift rule does not apply to this habitat. The chart is in the habitat's months.

Summary

Acanthus montanus, also known as bear's breech or mountain thistle and in Igbo; ogwu_agamevu (in Agbani, Enugu State Nigeria) is a species of flowering plant in the genus Acanthus. It is native to tropical Africa, growing in wet and shady places like stream borders in Sierra Leone in West Africa and from Benin to Chad, Zambia, and Angola in central Africa.

Quoted from Wikipedia, "Acanthus montanus", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads a sharp season: 70% of the median year's rain (1,914 mm of 2,473 mm) falls in May to October. The temperature curve is flat, 2.9 °C between the warmest and coldest month, so the growing-season rule does not infer a growing season from it. Months are the habitat's, northern hemisphere. The habitat lies within 10° of the equator, where the shift rule does not apply, so they are not shifted for a collection elsewhere.

Rain

2,473 mm in the median year at the habitat, 1,914 mm of it May to October. Wettest month July at 370 mm, driest month December at 29 mm. Across the grid cells of the range the year's total runs 1,483 mm to 2,950 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 2,569 mm, is the year's rain at the top of the page; the 2,473 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: 23 to 34 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 22, the highest 90th-percentile month 37).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is 19.9 °C, the absolute minimum 14.9 °C, no frost in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 32.8 °C. Monthly means: the coldest month's mean nightly low 22.2 °C in July and August (across the grid cells of the range 15.3 °C to 23.0 °C), the warmest month's mean daily high 31.5 °C in February (median year across the grid cells of the range, CHELSA). Cold floor: 19.9 °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: 64 to 70% 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 +35 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 Acanthus montanus through the yearWarmest month February, mean daily high 32 °C; coldest months July and August, mean nightly low 22.2 °C; 2,473 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.10°15°20°25°30°35°32.8° 99th-percentile day, NASA POWER14.9° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400500mm rainDLI 23–34RH 64–70%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 62 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 °C31 / 26–3332 / 27–3431 / 27–3331 / 26–3230 / 26–3028 / 26–2927 / 25–2827 / 25–2928 / 26–2929 / 25–2930 / 25–3131 / 25–32
Night °C23 / 18–2423 / 19–2524 / 20–2524 / 20–2523 / 19–2523 / 16–2422 / 15–2322 / 15–2322 / 17–2323 / 18–2423 / 19–2423 / 19–24
Rain mm30 / 10–17456 / 31–213129 / 86–247199 / 151–303270 / 124–294310 / 11–357370 / 3–491325 / 11–386343 / 62–477296 / 170–385116 / 37–37929 / 11–259
DLI33 / 32–3634 / 33–3732 / 31–3530 / 29–3428 / 27–3324 / 23–3223 / 22–3224 / 23–3425 / 24–3427 / 25–3229 / 28–3231 / 30–34
RH %64 / 54–6964 / 56–6866 / 62–6968 / 66–7068 / 65–7169 / 63–7268 / 60–7268 / 62–7269 / 66–7370 / 67–7267 / 65–7265 / 58–70
How this section is made
Each figure is the median across the 62 grid cells holding the 77 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 1665:3653 (6.725, 2.675). Over 44 years there: absolute minimum 14.9 °C, 1st-percentile night 19.9 °C, 99th-percentile day 32.8 °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 62 distinct grid cells holding 77 of the 77 in-range records; extremes and elevation at the typical cell 1665:3653 (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 6.50_2.500, lapse-corrected +35 m at 6.5 °C/km. Elevation: ETOPO 2022, 65 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.
NativeBenin, Nigeria, Sierra Leone, Burundi, Central African Republic, Cameroon, Congo, Gabon, Gulf of Guinea Is., Rwanda, Zaïre, Chad, Angola, Zambia · introduced: Mauritius, Costa Rica · 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 marker4.667, 9.417 · in the densest population, 128 records (36% of those in range)
Kew's description“subshrub or shrub” · “seasonally dry tropical” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 351 georeferenced records inside the native range; the climate across the range on the 77 of them placed to within 10 km; the map shows only the 327 openly licensed ones, which alone would put the marker 12 km away. 35 records outside the WCVP native range not used. 274 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 2° block of the 351 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Acanthus montanus, photograph 1did not loadAcanthus montanus, photograph 2did not loadAcanthus montanus, photograph 3did not loadAcanthus montanus, photograph 4did not loadAcanthus montanus, photograph 5did not loadAcanthus montanus, photograph 6did not load

Photographs: (c) Philippe Hornus, some rights reserved (CC BY) (2); author not stated, no rights reserved · CC0 (4).

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

Ficus barteri Ficus barteri Moraceae Photo: CC BY-SA, Ji-ElleDracaena arborea Dracaena arborea Tree dracaena Photo: CC BY, Lucy Keith-DiagneRaphia vinifera Raphia vinifera West African piassava palm Photo: Public domain, ToluayeAnubias barteri Anubias barteri Araceae Photo: Public domain, en:User:TsunamicarlosLasimorpha senegalensis Lasimorpha senegalensis Swamp Arum Photo: CC BY, pavlaki1968Piper guineense Piper guineense Benin pepper Photo: CC BY, William Stephens

Other Acanthus 13 in the reference

Acanthus arboreus Acanthus arboreus Acanthaceae Photo: CC BY-SA, Aboalfotooh Yemen WILD life Acanthus caroli-alexandri Acanthaceae Acanthus dioscoridis Acanthus dioscoridis Acanthaceae Photo: CC BY-SA, Dûrzan CîranoAcanthus ebracteatus Acanthus ebracteatus Sea Holly Photo: CC BY, Ong Jyh SengAcanthus eminens Acanthus eminens Acanthaceae Photo: CC0, author not statedAcanthus hirsutus Acanthus hirsutus Syrian acanthus Photo: CC BY, Michael, Antoni and Nihat HinczewskiAcanthus hungaricus Acanthus hungaricus Hungarian Bear’s-Breeches Photo: CC BY, Cristian BadoiuAcanthus ilicifolius Acanthus ilicifolius Holly mangrove Photo: CC BY, Richard LittauerAcanthus leucostachyus Acanthus leucostachyus Acanthaceae Photo: CC BY, Dmitry IvanovAcanthus mollis Acanthus mollis Bear's breech Photo: CC BY, Gianni Del Bufalo bygdbAcanthus polystachyus Acanthus polystachyus Bear's Breeches Photo: CC BY-SA, Tony RebeloAcanthus sennii Acanthus sennii Ethiopian acanthus Photo: CC BY, avocat all 14 ›

Names & registers

Also known as Acanthus barteri; Cheilopsis montana. (GBIF Backbone)

Kew accepts as species of their own Acanthus caudatus: 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
Acanthaceae
Described by
(Nees) T.Anderson
Native to
Benin, Nigeria, Sierra Leone +11
Wild records
351 in range · 327 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; 34 records within 1 km of a botanic garden, herbarium or zoo left out (28 at a botanic garden or arboretum, 6 at a herbarium; 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 6.50_2.500, lapse-corrected +35 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 44 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…