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Polystichum aculeatum; photograph (c) Daniel Buczkiewicz, some rights reserved (CC BY) CC BY(c) Daniel Buczkiewicz, some rights reserved (CC BY) · observed growing wild · 2026-09-21

Polystichum aculeatum (L.) Roth

Hard shield-fern

Dryopteridaceae · Denmark, Great Britain +40 · listed by its genus as a fern or moss

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Polystichum aculeatum, photograph (c) Daniel Buczkiewicz, some rights reserved (CC BY)Polystichum aculeatum, photograph (c) Daniel Buczkiewicz, some rights reserved (CC BY)Polystichum aculeatum, photograph (c) Daniel Buczkiewicz, some rights reserved (CC BY)Polystichum aculeatum, photograph (c) Daniel Buczkiewicz, some rights reserved (CC BY)Polystichum aculeatum, photograph author not stated, no rights reservedPolystichum aculeatum, photograph (c) FloraJenensis, some rights reserved (CC BY) 78 photographs ›
Habitat figures
Cold floor (1 night in 100)
-7.9°C
Record low -15.2 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
22°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,205mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
7–35DLI
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

Polystichum aculeatum, the hard shield-fern, is an evergreen fern native to Europe. It is most abundant in upland regions of the British Isles and western France, where it benefits from the combination of mild winters and moist summers, but also occurs more locally across most of Europe except northern Scandinavia, northern Russia; in the Mediterranean region it is confined to high altitudes. It grows on steep slopes in woodlands. it is sometimes considered an indicator of the presence of ancient woodlands.

Quoted from Wikipedia, "Polystichum aculeatum", CC BY-SA 4.0.

About the genus · Polystichum

Polystichum is a genus of ferns in the family Dryopteridaceae, subfamily Dryopteridoideae, according to the Pteridophyte Phylogeny Group classification of 2016. The genus has about 500 species and has a cosmopolitan distribution. The highest diversity is in eastern Asia, with about 208 species in China alone; the region from Mexico to Brazil has at least 100 additional species; Africa, North America, and Europe have much lower diversity. More on Wikipedia ›

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

Cultivation

Grouped as a fern or moss, listed under the genus Polystichum in the archetype table, and Kew describes it as “perennial”.

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (860 mm of 1,185 mm) takes 8 months, May to December. Mean temperature moves 18.2 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: November to June.

Rain

1,185 mm in the median year at the habitat, 860 mm of it May to December. Wettest month August at 121 mm, driest month February at 71 mm. Across the grid cells of the range the year's total runs 789 mm to 1,738 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,205 mm, is the year's rain at the top of the page; the 1,185 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: 7 to 35 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 4, the highest 90th-percentile month 39).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -7.9 °C, the absolute minimum -15.2 °C, 3,138 frost nights in 44 years, 71.3 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 29.4 °C. Monthly means: the coldest month's mean nightly low -4.0 °C in January (across the grid cells of the range -8.6 °C to 0.3 °C), the warmest month's mean daily high 22.0 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -7.9 °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: 59 to 66% 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 +343 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.

Group. Listed under the genus Polystichum in the archetype table, and Kew describes it as “perennial”. A group is taken only where Kew's description of the species agrees with the table's listing. The table gives no figure and no prose; the cold floor is the habitat's alone.

Climate across the habitat

Habitat months, northern hemisphere

Habitat climate of Polystichum aculeatum through the yearWarmest months July and August, mean daily high 22 °C; coldest month January, mean nightly low -4.0 °C; 1,185 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°frost29.4° 99th-percentile day, NASA POWER-15.2° lowest night in 44 years, NASA POWER°C · day and nightcold quarter050100150200mm rainDLI 7–35RH 59–66%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 485 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 °C3 / 0–65 / 1–68 / 5–1012 / 9–1417 / 14–1920 / 17–2222 / 19–2422 / 19–2418 / 15–2014 / 11–157 / 5–94 / 0–6
Night °C-4 / -9–0-4 / -8–00 / -4–33 / -1–58 / 4–911 / 8–1313 / 10–1513 / 10–1510 / 7–116 / 3–81 / -3–4-3 / -7–1
Rain mm84 / 44–12471 / 42–10688 / 53–13282 / 51–132112 / 67–165118 / 71–181118 / 71–199121 / 69–192107 / 65–16296 / 64–15792 / 60–14696 / 58–142
DLI8 / 5–1114 / 10–1721 / 16–2529 / 27–3334 / 32–3635 / 33–3835 / 32–3930 / 27–3322 / 18–2615 / 11–189 / 6–117 / 4–9
RH %65 / 60–6962 / 60–6661 / 59–6459 / 58–6260 / 58–6261 / 58–6360 / 57–6361 / 58–6463 / 60–6564 / 62–6766 / 62–6966 / 61–70
How this section is made
Each figure is the median across the 485 grid cells on land that hold in-range records (629 records in those cells; 3 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 926:4405 (43.675, 40.275). Over 44 years there: absolute minimum -15.2 °C, 1st-percentile night -7.9 °C, 99th-percentile day 29.4 °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 485 distinct grid cells holding 629 of the 632 in-range records (3 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 926:4405 (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 43.50_40.000, lapse-corrected +343 m at 6.5 °C/km. Elevation: ETOPO 2022, 879 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.
NativeDenmark, Great Britain, Ireland, Norway, Sweden, Austria, Belgium, Czechoslovakia, Germany, Hungary, Netherlands, Poland, Switzerland, Corse, France, Sardegna, Spain, Albania, Bulgaria, Greece, Italy, Romania, Yugoslavia, Baltic States, Krym, Central European Russia, Northwest European Russia, Ukraine, Algeria, Morocco, Canary Is., Madeira, Altay, Tadzhikistan, North Caucasus, Transcaucasus, Iran, Iraq, Lebanon-Syria, Turkey, Xinjiang, West Himalaya · introduced: Vanuatu · 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 marker47.742, 13.283 · in the densest population, 274 records (42% of those in range)
Kew's description“perennial” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 646 georeferenced records inside the native range; the climate across the range on the 629 of them in the land cells it reads, of 632 placed to within 10 km; the map shows only the 223 openly licensed ones, which alone would put the marker 348 km away. 14 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 646 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Polystichum aculeatum, photograph 1did not loadPolystichum aculeatum, photograph 2did not loadPolystichum aculeatum, photograph 3did not loadPolystichum aculeatum, photograph 4did not loadPolystichum aculeatum, photograph 5did not loadPolystichum aculeatum, photograph 6did not load

Photographs: (c) Daniel Buczkiewicz, some rights reserved (CC BY) (4); author not stated, no rights reserved · CC0; (c) FloraJenensis, some rights reserved (CC BY).

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

Salix purpurea Salix purpurea Purple willow Photo: CC BY, Мирослав СоболевGladiolus palustris Gladiolus palustris Marsh gladiolus Photo: CC BY, Christoph MoningPhyteuma spicatum Phyteuma spicatum Spiked Rampion Photo: CC BY, tetyanakuchmaBrachypodium pinnatum Brachypodium pinnatum Heath false-brome Photo: CC BY, Oleksandr ShynderAbies alba Abies alba European Silver fir Photo: CC BY, Thomas EbnerDianthus gratianopolitanus Dianthus gratianopolitanus Cheddar pink Photo: CC0, author not stated

Other Polystichum 43 in the reference

Polystichum acrostichoides Polystichum acrostichoides Christmas fern Photo: CC BY, Michael J. PapayPolystichum andersonii Polystichum andersonii Anderson's holly fern Photo: CC BY, Matt BergerPolystichum andinum Polystichum andinum Dryopteridaceae Photo: CC BY, Constanza Vargas VillegasPolystichum × bicknellii Polystichum × bicknellii Dryopteridaceae Photo: CC BY, Sean Frederick TuckPolystichum braunii Polystichum braunii Braun's holly fern Photo: CC BY, Oleg Kosterin Polystichum calderonense Monte Guilarte holly fern Polystichum dracomontanum Polystichum dracomontanum Dryopteridaceae Photo: CC0, author not statedPolystichum drepanum Polystichum drepanum Madeira Shield-Fern Photo: CC0, author not stated Polystichum × dycei Dryopteridaceae Polystichum falcinellum Polystichum falcinellum Madeira Sword-Fern Photo: CC BY, K.P. Polystichum grandifrons Dryopteridaceae Polystichum hancockii Polystichum hancockii Dryopteridaceae Photo: CC BY, Jacy Chen all 44 ›

Names & registers

Also known as Aetopteron aculeatum; Aspidium aculeatum; Aspidium aculeatum f. plukenetii; Aspidium aculeatum f. rotundatum; Aspidium aculeatum f. simplicius and 65 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Dryopteridaceae
Described by
(L.) Roth
Native to
Denmark, Great Britain, Ireland +39
Wild records
646 in range · 223 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 answeredasked 2026-10-22GBIF occurrence search API; 63 records within 1 km of a botanic garden, herbarium or zoo left out (49 at a botanic garden or arboretum, 14 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 43.50_40.000, lapse-corrected +343 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22IPNI and POWO linked by Kew's number for Polystichum aculeatum (L.) Roth (the item's: IPNI 17205720-1, POWO 17413440-1)
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 10 datasets via GBIF.org; each carries its own licence.

Cultifolio

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