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Athyrium angustum; photograph (c) Karen Saunders, some rights reserved (CC BY) CC BY(c) Karen Saunders, some rights reserved (CC BY) · observed growing wild · 2026-09-26

Athyrium angustum (Willd.) C.Presl

Subarctic lady fern; Northeastern lady fern; Northern lady fern

Athyriaceae · Greenland, Manitoba +36 · listed by its genus as a fern or moss

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Athyrium angustum, photograph (c) Karen Saunders, some rights reserved (CC BY)Athyrium angustum, photograph (c) Karen Saunders, some rights reserved (CC BY)Athyrium angustum, photograph (c) Karen Saunders, some rights reserved (CC BY)Athyrium angustum, photograph (c) Andrew Sebastian, some rights reserved (CC BY)Athyrium angustum, photograph (c) Patrick Comins, some rights reserved (CC BY)Athyrium angustum, photograph (c) kursic, some rights reserved (CC BY) 68 photographs ›
Habitat figures
Cold floor (1 night in 100)
-26.6°C
Record low -40.7 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
25°C
Jul at the habitat CHELSA
Rain a year (median across the range)
1,039mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
9–39DLI
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

Athyrium angustum, the northern lady fern or subarctic lady fern, is a fern native to northeastern North America. It was long included in the superspecies Athyrium filix-femina, but is now largely recognized as a distinct species.

Quoted from Wikipedia, "Athyrium angustum", CC BY-SA 4.0.

About the genus · Athyrium

Athyrium (lady-fern) is a genus of about 180 species of terrestrial ferns, with a cosmopolitan distribution. It is placed in the family Athyriaceae, in the order Polypodiales. Its genus name is from Greek a- ('without') and Latinized Greek thyreos ('shield'), describing its inconspicuous indusium . More on Wikipedia ›

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

Cultivation

Grouped as a fern or moss, listed under the genus Athyrium 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 (782 mm of 1,069 mm) takes 8 months, April to November. Mean temperature moves 28.1 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: October to May.

Rain

1,069 mm in the median year at the habitat, 782 mm of it April to November. Wettest month June at 107 mm, driest month February at 65 mm. Across the grid cells of the range the year's total runs 831 mm to 1,366 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,039 mm, is the year's rain at the top of the page; the 1,069 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: 9 to 39 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 7, the highest 90th-percentile month 41).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -26.6 °C, the absolute minimum -40.7 °C, 6,888 frost nights in 44 years, 156.5 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 32.7 °C. Monthly means: the coldest month's mean nightly low -11.6 °C in January (across the grid cells of the range -15.9 °C to -6.7 °C), the warmest month's mean daily high 25.4 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -26.6 °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: 56 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 -24 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 Athyrium 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 Athyrium angustum through the yearWarmest month July, mean daily high 25 °C; coldest month January, mean nightly low -11.6 °C; 1,069 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.-60°-40°-20°0°20°40°frost32.7° 99th-percentile day, NASA POWER-40.7° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 9–39RH 56–63%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 1382 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 °C-3 / -7–1-1 / -6–34 / 0–812 / 7–1518 / 13–2023 / 19–2525 / 22–2824 / 22–2720 / 18–2313 / 11–166 / 3–100 / -4–4
Night °C-12 / -16–-7-10 / -14–-6-5 / -8–-22 / -1–48 / 5–1014 / 11–1617 / 15–1916 / 14–1812 / 10–156 / 4–80 / -3–3-7 / -12–-3
Rain mm72 / 26–10065 / 25–9768 / 43–11586 / 65–11697 / 79–117107 / 84–129104 / 82–12998 / 82–125101 / 87–12198 / 71–13091 / 51–12682 / 34–119
DLI11 / 10–1318 / 16–1925 / 24–2632 / 30–3336 / 35–3939 / 37–4138 / 36–4133 / 32–3525 / 23–2717 / 15–2011 / 9–139 / 7–11
RH %63 / 58–6661 / 57–6458 / 56–6156 / 54–5857 / 55–5959 / 56–6159 / 57–6260 / 59–6260 / 58–6260 / 57–6261 / 59–6463 / 58–67
How this section is made
Each figure is the median across the 1382 grid cells holding the 1615 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 915:1827 (44.225, -88.625). Over 44 years there: absolute minimum -40.7 °C, 1st-percentile night -26.6 °C, 99th-percentile day 32.7 °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 1382 distinct grid cells holding 1615 of the 1615 in-range records; extremes and elevation at the typical cell 915:1827 (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 44.00_-88.750, lapse-corrected -24 m at 6.5 °C/km. Elevation: ETOPO 2022, 235 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.
NativeGreenland, Manitoba, Saskatchewan, Labrador, New Brunswick, Newfoundland, Nova Scotia, Ontario, Prince Edward I., Québec, Colorado, Illinois, Iowa, Minnesota, Missouri, North Dakota, South Dakota, Wisconsin, Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Delaware, Kentucky, Maryland, North Carolina, Tennessee, Virginia, District of Columbia · 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 marker43.429, -72.372 · in the densest population, 1011 records (53% 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 1907 georeferenced records inside the native range; the climate across the range on the 1615 of them placed to within 10 km; the map shows only the 515 openly licensed ones, which alone would put the marker 69 km away. 13 records outside the WCVP native range not used. 292 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 4° block of the 1907 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Athyrium angustum, photograph 1did not loadAthyrium angustum, photograph 2did not loadAthyrium angustum, photograph 3did not loadAthyrium angustum, photograph 4did not loadAthyrium angustum, photograph 5did not loadAthyrium angustum, photograph 6did not load

Photographs: (c) Karen Saunders, some rights reserved (CC BY) (3); (c) Andrew Sebastian, some rights reserved (CC BY); (c) Patrick Comins, some rights reserved (CC BY); (c) kursic, some rights reserved (CC BY).

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

Potamogeton amplifolius Potamogeton amplifolius Large-leaved pondweed Photo: CC BY, Steven BodzinSolidago squarrosa Solidago squarrosa Stout goldenrod Photo: CC BY, Henrique PachecoCarex pedunculata Carex pedunculata Longstalk sedge Photo: CC BY, Dustin SniderLycopus uniflorus Lycopus uniflorus Northern water-horehound Photo: CC BY, betsyyyyCrataegus macracantha Crataegus macracantha Large-thorn hawthorn Photo: CC0, author not statedSymphyotrichum puniceum Symphyotrichum puniceum Red-stalked Michaelmas-daisy Photo: CC0, author not stated

Other Athyrium 13 in the reference

Athyrium americanum Athyrium americanum Alpine ladyfern Photo: CC BY, James H. ThomasAthyrium asplenioides Athyrium asplenioides Southern lady fern Photo: CC BY, David Wilkins Athyrium crenulatoserrulatum Aspleniaceae Athyrium cyclosorum Athyrium cyclosorum Western Lady Fern Photo: CC0, Ellyne GeurtsAthyrium distentifolium Athyrium distentifolium Aspleniaceae Photo: CC BY-SA, Jerzy OpiołaAthyrium filix-femina Athyrium filix-femina Lady-fern Photo: CC0, author not stated Athyrium iseanum Narrow-leaf ladyfern Athyrium microphyllum Athyrium microphyllum Akolea Photo: CC0, author not statedAthyrium otophorum Athyrium otophorum Eared lady fern Photo: CC0, author not statedAthyrium rubripes Athyrium rubripes Athyriaceae Photo: CC BY, Violetta DzizyurovaAthyrium strigillosum Athyrium strigillosum Athyriaceae Photo: CC BY, Jacy ChenAthyrium vidalii Athyrium vidalii Vidal’s ladyfern Photo: CC BY-SA, harum.koh all 14 ›

Names & registers

Also known as Aspidium angustum; Asplenium elatius; Asplenium filix-femina var. angustum; Asplenium michauxii; Athyrium angustum f. confertum and 27 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Athyriaceae
Described by
(Willd.) C.Presl
Native to
Greenland, Manitoba, Saskatchewan +35
Wild records
1907 in range · 515 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; 41 records within 1 km of a botanic garden, herbarium or zoo left out (33 at a botanic garden or arboretum, 3 at a herbarium, 5 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 44.00_-88.750, lapse-corrected -24 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 45 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…