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Polemonium villosum; photograph Elisa Pietikäinen, CC BY-SA, via GBIF CC BY-SAElisa Pietikäinen, CC BY-SA, via GBIF

Polemonium villosum Rudolph ex Georgi

Tall Jacob's-ladder

Polemoniaceae · Finland, Norway +21

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Polemonium villosum, photograph Elisa Pietikäinen, CC BY-SA, via GBIFPolemonium villosum, photograph Elisa Pietikäinen, CC BY-SA, via GBIFPolemonium villosum, photograph Gunnar Engan, CC BY, via GBIFPolemonium villosum, photograph Frank Grønningsæter, CC BY, via GBIFPolemonium villosum, photograph Gunnar Engan, CC BY, via GBIFPolemonium villosum, photograph Elisa Pietikäinen, CC BY-SA, via GBIF 14 photographs ›
Habitat figures
Cold floor (1 night in 100)
-25.6°C
Record low -35.4 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
16°C
Jul at the habitat CHELSA
Rain a year (median across the range)
712mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
0–32DLI
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 May to November, 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 acutiflorum (syn. P. villosum), known as tall Jacob's-ladder, is a flowering plant in the family Polemoniaceae. It is native to much of the northern hemisphere.

Quoted from Wikipedia, "Polemonium acutiflorum", CC BY-SA 4.0; its title is one of this species' older names (GBIF Backbone), which is the proof that the article is this species'.

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 (505 mm of 701 mm) falls in May to November, warmer than the year (wet-season mean 5.5 °C against a yearly mean of -0.4 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: November to May.

Rain

701 mm in the median year at the habitat, 505 mm of it May to November. Wettest month July at 106 mm, driest month April at 36 mm. Across the grid cells of the range the year's total runs 604 mm to 836 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 712 mm, is the year's rain at the top of the page; the 701 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 32 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 34).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -25.6 °C, the absolute minimum -35.4 °C, 11,084 frost nights in 44 years, 251.9 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 18.9 °C. Monthly means: the coldest month's mean nightly low -15.0 °C in January (across the grid cells of the range -16.7 °C to -14.1 °C), the warmest month's mean daily high 16.2 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -25.6 °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: 58 to 74% 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 +49 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 villosum through the yearWarmest month July, mean daily high 16 °C; coldest month January, mean nightly low -15.0 °C; 701 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.-40°-30°-20°-10°0°10°20°frost18.9° 99th-percentile day, NASA POWER-35.4° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 0–32RH 58–74%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 1037 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-9 / -11–-9-9 / -11–-9-5 / -8–-41 / -3–37 / 3–913 / 10–1516 / 13–1814 / 11–158 / 6–91 / -1–2-5 / -7–-4-8 / -10–-7
Night °C-15 / -17–-14-14 / -16–-14-10 / -13–-9-6 / -8–-5-1 / -3–16 / 3–79 / 7–118 / 5–93 / 1–4-3 / -6–-1-10 / -13–-8-14 / -16–-13
Rain mm44 / 31–6437 / 27–4937 / 27–4636 / 30–4348 / 38–6075 / 63–89106 / 95–13493 / 82–10768 / 56–7764 / 54–7751 / 38–6342 / 31–61
DLI0 / 0–03 / 2–311 / 10–1223 / 22–2530 / 29–3432 / 31–3327 / 26–2819 / 18–2010 / 10–124 / 3–41 / 0–10
RH %73 / 70–7672 / 70–7468 / 66–7162 / 60–6760 / 57–6558 / 56–6260 / 59–6463 / 62–6666 / 65–6970 / 68–7374 / 71–7574 / 71–76
How this section is made
Each figure is the median across the 1037 grid cells on land that hold in-range records (1304 records in those cells; 2 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 473:3925 (66.325, 16.275). Over 44 years there: absolute minimum -35.4 °C, 1st-percentile night -25.6 °C, 99th-percentile day 18.9 °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 1037 distinct grid cells holding 1304 of the 1306 in-range records (2 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 473:3925 (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 66.50_16.250, lapse-corrected +49 m at 6.5 °C/km. Elevation: ETOPO 2022, 864 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.
NativeFinland, Norway, Sweden, North European Russia, Buryatiya, Irkutsk, Krasnoyarsk, West Siberia, Yakutskiya, Kamchatka, Khabarovsk, Kuril Is., Magadan, Primorye, Inner Mongolia, Manchuria, Korea, Aleutian Is., Alaska, Northwest Territories, Yukon, Alberta, 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 marker68.541, 26.396 · in the densest population, 845 records (55% 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 1524 georeferenced records inside the native range; the climate across the range on the 1304 of them in the land cells it reads, of 1306 placed to within 10 km; the map shows only the 1512 openly licensed ones, which alone would put the marker in the same place. 4 records outside the WCVP native range not used. 218 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 1524 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 villosum, photograph 1did not loadPolemonium villosum, photograph 2did not loadPolemonium villosum, photograph 3did not loadPolemonium villosum, photograph 4did not loadPolemonium villosum, photograph 5did not loadPolemonium villosum, photograph 6did not load

Photographs: Elisa Pietikäinen, CC BY-SA, via GBIF (3); Gunnar Engan, CC BY, via GBIF (2); Frank Grønningsæter, CC BY, via GBIF.

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

Ranunculus propinquus Ranunculus propinquus Ranunculaceae Photo: CC BY, Urgamal MagsarLycopodium lagopus Lycopodium lagopus One-cone clubmoss Photo: CC BY, Tanner BarnharstPinguicula villosa Pinguicula villosa Hairy butterwort Photo: CC BY, Andreas SchneiderAstragalus norvegicus Astragalus norvegicus Fabaceae Photo: CC BY, Aleksandr NovikovLuzula parviflora Luzula parviflora Millet woodrush Photo: CC0, author not statedCarex capitata Carex capitata Capitate sedge Photo: CC BY, Ida B D Jacobsen

Other Polemonium 19 in the reference

Polemonium boreale Polemonium boreale Boreal Jacob's-ladder Photo: CC BY, Trevor Van LoonPolemonium 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 all 20 ›

Names & registers

Also known as Polemonium acutiflorum; Polemonium acutiflorum f. lacteum; Polemonium acutiflorum subsp. diminutum; Polemonium caeruleum subsp. racemosum; Polemonium caeruleum subsp. villosum and 15 more. (GBIF Backbone)

Kew accepts as species of their own Polemonium campanulatum: 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)

GBIFPOWOIPNIWFOWikidataWikipedia

The record

Family
Polemoniaceae
Described by
Rudolph ex Georgi
Native to
Finland, Norway, Sweden +20
Wild records
1524 in range · 1512 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
Habitat climate climate answeredasked 2026-10-22
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-22NASA POWER (MERRA-2) daily 1981–2024, cell 66.50_16.250, lapse-corrected +49 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22found by its label; its IPNI identifier 690035-1 is Kew's for Polemonium villosum Rudolph ex Georgi
Wikipedia wikipedia answeredasked 2026-10-22Wikipedia redirects Polemonium villosum to Polemonium acutiflorum, an older name of this species (Polemonium acutiflorum)
iNaturalist taxon inat.taxon not asked
iNaturalist photographs, wild inat.photos.wild not asked
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 49 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…