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Acaena inermis; photograph (c) John Barkla, some rights reserved (CC BY) CC BY(c) John Barkla, some rights reserved (CC BY) · observed growing wild · 2026-05-20

Acaena inermis Hook.f.

Spineless Acaena; Mountain bidibid

Rosaceae · New Zealand North, New Zealand South

Cited as Kew's World Checklist cites it, Acaena inermis Hook.f.: GBIF's backbone key for this page carries the name with another author, Hook.fil.

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Acaena inermis, photograph (c) Mike King, some rights reserved (CC BY)Acaena inermis, photograph author not stated, no rights reservedAcaena inermis, photograph (c) Mel Whiting, some rights reserved (CC BY)Acaena inermis, photograph (c) Mel Whiting, some rights reserved (CC BY)Acaena inermis, photograph (c) Frank Ashwood, some rights reserved (CC BY)Acaena inermis, photograph (c) kiwialli, some rights reserved (CC BY) 73 photographs ›
Habitat figures
Cold floor (1 night in 100)
-4.7°C
Record low -10.6 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
16°C
Jan and Feb at the habitat CHELSA
Rain a year (median across the range)
1,894mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
9–41DLI
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

Acaena inermis, the spineless acaena, is a species of flowering plant in the family Rosaceae, endemic to New Zealand and introduced to Great Britain. Its common names include spineless bidibid and blue mountain bidibid. A mat-forming perennial useful as a ground cover, its cultivar 'Purpurea' is widely available from commercial suppliers.

Quoted from Wikipedia, "Acaena inermis", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (1,356 mm of 1,911 mm) takes 8 months, May to December. Mean temperature moves 11.8 °C between the warmest and coldest month. Months are the habitat's, southern hemisphere; shifted six months for a northern-hemisphere collection: November to June.

Rain

1,911 mm in the median year at the habitat, 1,356 mm of it May to December. Wettest month October at 192 mm, driest month February at 118 mm. Across the grid cells of the range the year's total runs 812 mm to 3,901 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,894 mm, is the year's rain at the top of the page; the 1,911 mm here is the median year's, the twelve monthly medians added, which the rain rule reads. Habitat calendar, southern hemisphere; median year across the grid cells of the range, CHELSA.

Light

Open sky over the habitat: 9 to 41 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 8, the highest 90th-percentile month 42).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -4.7 °C, the absolute minimum -10.6 °C, 4,153 frost nights in 44 years, 94.4 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 25.6 °C. Monthly means: the coldest month's mean nightly low -3.7 °C in July (across the grid cells of the range -6.7 °C to -0.9 °C), the warmest month's mean daily high 15.9 °C in January (median year across the grid cells of the range, CHELSA). Cold floor: -4.7 °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: 63 to 67% 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 -41 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, southern hemisphere

Habitat climate of Acaena inermis through the yearWarmest months January and February, mean daily high 16 °C; coldest month July, mean nightly low -3.7 °C; 1,911 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, southern hemisphere.-20°-10°0°10°20°30°frost25.6° 99th-percentile day, NASA POWER-10.6° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400mm rainDLI 9–41RH 63–67%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 249 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 °C16 / 13–2016 / 13–1914 / 11–1711 / 8–147 / 3–103 / 0–72 / -1–63 / 0–86 / 2–119 / 5–1312 / 8–1514 / 11–18
Night °C7 / 4–107 / 5–106 / 3–83 / 0–60 / -3–3-3 / -6–0-4 / -7–-1-3 / -5–0-1 / -4–21 / -2–43 / 0–66 / 3–9
Rain mm151 / 73–337118 / 63–250142 / 72–314144 / 59–302159 / 68–322174 / 64–334157 / 67–276159 / 61–305167 / 58–351192 / 71–388165 / 65–328183 / 85–399
DLI41 / 38–4234 / 32–3627 / 25–2918 / 16–2012 / 10–139 / 8–1111 / 9–1316 / 14–1824 / 22–2732 / 29–3439 / 35–4140 / 37–42
RH %63 / 58–6663 / 59–6664 / 60–6764 / 61–6866 / 61–7067 / 62–7166 / 61–7167 / 62–7066 / 60–6965 / 60–6963 / 59–6764 / 59–68
How this section is made
Each figure is the median across the 249 grid cells holding the 428 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 2706:6985 (-45.325, 169.275). Over 44 years there: absolute minimum -10.6 °C, 1st-percentile night -4.7 °C, 99th-percentile day 25.6 °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 249 distinct grid cells holding 428 of the 428 in-range records; extremes and elevation at the typical cell 2706:6985 (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 -45.50_169.375, lapse-corrected -41 m at 6.5 °C/km. Elevation: ETOPO 2022, 643 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.
NativeNew Zealand North, New Zealand South · introduced: Great Britain · 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 marker-43.201, 171.67 · in the densest population, 372 records (67% of those in range)
Kew's description“subshrub” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 555 georeferenced records inside the native range; the climate across the range on the 428 of them placed to within 10 km; the map shows only the 251 openly licensed ones, which alone would put the marker 26 km away. 89 records outside the WCVP native range not used. 127 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 555 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Acaena inermis, photograph 1did not loadAcaena inermis, photograph 2did not loadAcaena inermis, photograph 3did not loadAcaena inermis, photograph 4did not loadAcaena inermis, photograph 5did not loadAcaena inermis, photograph 6did not load

Photographs: (c) Mike King, some rights reserved (CC BY); author not stated, no rights reserved · CC0; (c) Mel Whiting, some rights reserved (CC BY) (2); (c) Frank Ashwood, some rights reserved (CC BY); (c) kiwialli, some rights reserved (CC BY).

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

Anisotome filifolia Anisotome filifolia Apiaceae Photo: CC0, author not statedEpilobium melanocaulon Epilobium melanocaulon Onagraceae Photo: CC BY, Jeff YoungVeronica tetrasticha Veronica tetrasticha Plantaginaceae Photo: CC BY-SA, Christopher StephensPittosporum patulum Pittosporum patulum Pitpat Photo: CC0, author not statedLuzula rufa Luzula rufa Juncaceae Photo: CC BY, Lorraine CookChionochloa rigida Chionochloa rigida Narrow leaved Snow Tussock Photo: CC BY, rempson

Other Acaena 27 in the reference

Acaena anserinifolia Acaena anserinifolia Bronze pirri-pirri-bur Photo: CC BY, Stephen HartleyAcaena antarctica Acaena antarctica Antarctic prickly-burr Photo: CC BY, Cody HinchliffAcaena argentea Acaena argentea Rosaceae Photo: CC BY, Bruno AvilezAcaena buchananii Acaena buchananii Rosaceae Photo: CC BY, Jon SullivanAcaena caesiiglauca Acaena caesiiglauca Glaucous pirri-pirri-bur Photo: CC BY, Mel WhitingAcaena caespitosa Acaena caespitosa Rosaceae Photo: CC BY, Felipe HortonAcaena cylindristachya Acaena cylindristachya Rosaceae Photo: CC0, author not statedAcaena elongata Acaena elongata Rosaceae Photo: CC BY, Erick Vélez SánchezAcaena eupatoria Acaena eupatoria Rosaceae Photo: CC BY, Diego BarbozaAcaena fissistipula Acaena fissistipula Rosaceae Photo: CC BY, Pieter PelserAcaena glabra Acaena glabra Rosaceae Photo: CC0, author not statedAcaena juvenca Acaena juvenca Rosaceae Photo: CC BY, Mel Whiting all 28 ›

Names & registers

Also known as Acaena inermis var. pallideolivacea; Acaena microcephala f. breviscapa; Acaena microcephala f. longiscapa; Acaena microcephala f. pilosicaulis; Acaena microcephala f. subglabriuscula and 4 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Rosaceae
Described by
Hook.f.
Native to
New Zealand North, New Zealand South
Wild records
555 in range · 251 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 2026-10-21GBIF's key 5370687 is Acaena inermis Hook.fil.; the page links Kew's Acaena inermis Hook.f., and the name is cited as Kew cites it
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; 9 records within 1 km of a botanic garden, herbarium or zoo left out (5 at a botanic garden or arboretum, 3 at a herbarium, 1 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 -45.50_169.375, lapse-corrected -41 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 24 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…