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Polemonium boreale; photograph author not stated, no rights reserved CC0author not stated, no rights reserved · observed growing wild · 2026-07-13

Polemonium boreale Adams

Boreal Jacob's-ladder; Northern Jacob's-ladder

Polemoniaceae · Norway, Svalbard +14

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Polemonium boreale, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium boreale, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium boreale, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium boreale, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium boreale, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium boreale, photograph (c) Jacek Pietruszewski, some rights reserved (CC BY) 80 photographs ›
Habitat figures
Cold floor (1 night in 100)
-36.7°C
Record low -46.3 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
13°C
Jul at the habitat CHELSA
Rain a year (median across the range)
501mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
0–36DLI
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 summers: the rain comes June to December, read as a summer growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Polemonium boreale, the northern Jacob's-ladder or boreal Jacobs-ladder, is a plant native to most of the high arctic. In Greenland it is found only in a small area on the east coast. It is not very common.

Quoted from Wikipedia, "Polemonium boreale", CC BY-SA 4.0.

About the genus · Polemonium

Polemonium, commonly called Jacob's ladders or Jacob's-ladders, is a genus of between 25 and 40 species of flowering plants in the family Polemoniaceae, native to cool temperate to arctic regions of the Northern Hemisphere. One species, Polemonium micranthum, also occurs in the southern Andes in South America. Many of the species grow at high altitudes, in mountainous areas. More on Wikipedia ›

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

Cultivation

Seasons

The rain rule reads a summer growing season: 70% of the median year's rain (366 mm of 512 mm) falls in June to December, warmer than the year (wet-season mean -3.1 °C against a yearly mean of -8.6 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: December to June.

Rain

512 mm in the median year at the habitat, 366 mm of it June to December. Wettest month August at 72 mm, driest month April at 26 mm. Across the grid cells of the range the year's total runs 330 mm to 1,131 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 501 mm, is the year's rain at the top of the page; the 512 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: 0 to 36 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 0, the highest 90th-percentile month 40).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -36.7 °C, the absolute minimum -46.3 °C, 9,677 frost nights in 44 years, 219.9 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 29.3 °C. Monthly means: the coldest month's mean nightly low -26.5 °C in January (across the grid cells of the range -35.8 °C to -16.2 °C), the warmest month's mean daily high 13.2 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -36.7 °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 75% 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 -489 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 Polemonium boreale through the yearWarmest month July, mean daily high 13 °C; coldest month January, mean nightly low -26.5 °C; 512 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°frost29.3° 99th-percentile day, NASA POWER-46.3° lowest night in 44 years, NASA POWER°C · day and nightcold quarter050100150200mm rainDLI 0–36RH 63–75%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 753 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-21 / -30–-11-20 / -29–-10-15 / -23–-6-9 / -14–1-1 / -5–78 / 2–1513 / 6–1811 / 5–154 / 0–9-6 / -11–2-14 / -23–-5-18 / -28–-9
Night °C-27 / -36–-16-26 / -35–-16-22 / -30–-12-15 / -21–-6-6 / -9–02 / -1–76 / 3–105 / 1–9-1 / -4–4-11 / -17–-2-19 / -29–-10-24 / -34–-14
Rain mm36 / 14–7228 / 12–6328 / 11–6126 / 12–6328 / 17–7547 / 22–10170 / 35–13872 / 41–15556 / 35–13044 / 27–12137 / 19–9440 / 15–81
DLI0 / 0–43 / 0–1012 / 6–2126 / 21–3236 / 33–4036 / 33–4030 / 27–3319 / 17–2511 / 7–184 / 1–111 / 0–50 / 0–3
RH %75 / 64–9274 / 63–9371 / 61–8468 / 59–7665 / 58–6964 / 57–6963 / 59–6965 / 61–7066 / 62–7069 / 64–7573 / 64–8674 / 64–90
How this section is made
Each figure is the median across the 753 grid cells on land that hold in-range records (1016 records in those cells; 11 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 721:5799 (53.925, 109.975). Over 44 years there: absolute minimum -46.3 °C, 1st-percentile night -36.7 °C, 99th-percentile day 29.3 °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 753 distinct grid cells holding 1016 of the 1028 in-range records (11 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 721:5799 (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 54.00_110.000, lapse-corrected -489 m at 6.5 °C/km. Elevation: ETOPO 2022, 606 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.
NativeNorway, Svalbard, North European Russia, Buryatiya, Krasnoyarsk, West Siberia, Yakutskiya, Kamchatka, Khabarovsk, Kuril Is., Magadan, Alaska, Greenland, Northwest Territories, Yukon, British 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 marker78.214, 15.611 · in the densest population, 207 records (13% of those in range)
Kew's description“perennial” · “subalpine or subarctic” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 1648 georeferenced records inside the native range; the climate across the range on the 1016 of them in the land cells it reads, of 1028 placed to within 10 km; the map shows only the 1286 openly licensed ones, which alone would put the marker 1 km away. 32 records outside the WCVP native range not used. 620 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 1648 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Polemonium boreale, photograph 1did not loadPolemonium boreale, photograph 2did not loadPolemonium boreale, photograph 3did not loadPolemonium boreale, photograph 4did not loadPolemonium boreale, photograph 5did not loadPolemonium boreale, photograph 6did not load

Photographs: (c) Trevor Van Loon, some rights reserved (CC BY) (5); (c) Jacek Pietruszewski, some rights reserved (CC BY).

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

Eritrichium villosum Eritrichium villosum Boraginaceae Photo: CC BY, Илья РуденкоArtemisia borealis Artemisia borealis Boreal sage Photo: CC0, Julianne OuromLagotis glauca Lagotis glauca Glaucous weaselsnout Photo: CC BY, Ingvild RiskaPhysaria arctica Physaria arctica Arctic bladderpod Photo: CC0, author not statedSalix nummularia Salix nummularia Coin-leaf willow Photo: CC BY, Valerii GlazunovOreomecon lapponica Oreomecon lapponica Papaveraceae Photo: CC BY, Takeo Goto

Other Polemonium 19 in the reference

Polemonium brandegeei Polemonium brandegeei Brandegee's Jacob's-ladder Photo: CC BY, Dan VickersPolemonium caeruleum Polemonium caeruleum Jacob's-ladder Photo: CC BY, amantedarmaninPolemonium californicum Polemonium californicum California Jacob's ladder Photo: CC BY, John BrewPolemonium carneum Polemonium carneum Oregon polemonium Photo: CC0, author not statedPolemonium caucasicum Polemonium caucasicum Polemoniaceae Photo: CC BY, Yeskendir SatekovPolemonium chartaceum Polemonium chartaceum Mason's sky-pilot Photo: CC BY, Trevor Van Loon Polemonium chinense Chinese Jacob's-ladder Polemonium elegans Polemonium elegans Elegant Jacob's-ladder Photo: CC BY, i like lizardsPolemonium eximium Polemonium eximium Sierra Nevada Sky Pilot Photo: CC0, author not statedPolemonium foliosissimum Polemonium foliosissimum Leafy Jacob's-ladder Photo: CC BY, Daughter Dad Polemonium lacustre Polemoniaceae Polemonium occidentale Polemonium occidentale Western Jacob's-ladder Photo: CC0, author not stated all 20 ›

Names & registers

Also known as Polemonium arcticum; Polemonium boreale subsp. boreale; Polemonium boreale subsp. genuinum; Polemonium boreale subsp. humile; Polemonium boreale subsp. hyperboreum and 28 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Polemoniaceae
Described by
Adams
Native to
Norway, Svalbard, North European Russia +13
Wild records
1648 in range · 1286 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 answeredas of 2026-10-21GBIF occurrence download https://doi.org/10.15468/dl.hbdw64, of 2026-10-21; 1 record within 1 km of a botanic garden, herbarium or zoo left out (1 at a botanic garden or arboretum; 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 54.00_110.000, lapse-corrected -489 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22
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 77 datasets via GBIF.org; each carries its own licence.

Cultifolio

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