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Polemonium chartaceum; photograph (c) Trevor Van Loon, some rights reserved (CC BY) CC BY(c) Trevor Van Loon, some rights reserved (CC BY) · observed growing wild · 2023-08-26

Polemonium chartaceum H.Mason

Mason's sky-pilot; White Mountain sky-pilot; Mason's Jacob's-ladder; White Mountains sky pilot

Polemoniaceae · California, Nevada

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Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY)Polemonium chartaceum, photograph (c) Trevor Van Loon, some rights reserved (CC BY) 31 photographs ›
Habitat figures
Coldest month, mean nightly low
-14.7°C
Feb at the habitat, not a floor; extremes not used (the weather cell's ground is too far off) CHELSA
Warmest month, mean daily high
23°C
Jul at the habitat CHELSA
Rain a year (median across the range)
514mm
10 months of 25 mm or more in the median year CHELSA
Open-sky light
18–53DLI
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 winters: the rain comes November to May, with nights below freezing; no growing season read. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Polemonium chartaceum is a rare species of flowering plant in the phlox family known by the common names Mason's Jacob's-ladder and Mason's sky pilot. It is native to California, where it has a disjunct distribution. It occurs in the Klamath Mountains as well as the ranges east of the Sierra Nevada, including the White Mountains, where its distribution extends just into Nevada. It is a plant of high elevations, growing in exposed, rocky mountain slope habitat such as talus and alpine fellfields.

Quoted from Wikipedia, "Polemonium chartaceum", 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 rainy season and no growing season: 70% of the median year's rain (363 mm of 491 mm) falls in November to May, the cooler part of the year, but the mean nightly low is below freezing in February, March, April, May, June, December and January, so the rule reads no growing season from it. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: May to November.

Rain

491 mm in the median year at the habitat, 363 mm of it November to May. Wettest month January at 63 mm, driest month September at 23 mm. Across the grid cells of the range the year's total runs 359 mm to 1,749 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 514 mm, is the year's rain at the top of the page; the 491 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: 18 to 53 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 14, the highest 90th-percentile month 55).

Warmth and air
Temperature

Monthly means: the coldest month's mean nightly low -14.7 °C in February (across the grid cells of the range -16.3 °C to -9.1 °C), the warmest month's mean daily high 22.5 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: none read. The nearest figure is -14.7 °C, the coldest month's mean nightly low, February, in the median year (CHELSA); a month's mean of its nightly lows is warmer than the nights a floor is read from. The daily extremes were read at a weather cell whose ground is too far above or below the typical spot to correct for, and are not used.

Humidity

Relative humidity at the habitat: 40 to 50% 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. CHELSA monthly means, median year across the grid cells of the range. No cold floor is read without a daily extremes series; the coldest month's mean nightly low named in its sentence is not one. 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 chartaceum through the yearWarmest month July, mean daily high 23 °C; coldest month February, mean nightly low -14.7 °C; 491 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA. Habitat months, northern hemisphere.-20°-10°0°10°20°30°frost°C · day and nightcold quarter0100200300400mm rainDLI 18–53RH 40–50%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 11 habitat cells, CHELSA cold quarter: the three months around the coldest month's mean nightly low DLI, mol/m²/dayRH %each on its own scale
Figures by month
JanFebMarAprMayJunJulAugSepOctNovDec
Day °C-4 / -7–-1-4 / -6–0-1 / -3–45 / 2–811 / 9–1417 / 16–2023 / 20–2521 / 19–2416 / 14–209 / 7–132 / -1–5-4 / -6–-1
Night °C-15 / -17–-9-15 / -16–-9-12 / -13–-8-9 / -11–-4-3 / -5–13 / 1–68 / 6–107 / 5–103 / 1–6-4 / -5–0-10 / -11–-6-15 / -16–-10
Rain mm63 / 43–30059 / 43–25358 / 41–22043 / 33–12042 / 31–7724 / 16–3827 / 15–3425 / 16–3123 / 15–3729 / 23–10241 / 29–24057 / 41–327
DLI20 / 16–2327 / 22–3037 / 32–4045 / 41–4750 / 47–5253 / 52–5553 / 52–5349 / 47–4941 / 39–4331 / 28–3422 / 18–2518 / 14–21
RH %47 / 45–5450 / 47–5549 / 47–5749 / 48–5648 / 46–5243 / 41–4640 / 39–4340 / 40–4343 / 41–4544 / 44–4945 / 44–5447 / 45–54

The daily extremes were not used: the correction for elevation, +1125 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's. So no cold floor is read for this species, and the coldest month's mean nightly low is not taken as one. What that cell gave, so corrected, over 44 years: absolute minimum -34.3 °C, 1st-percentile night -26.0 °C.

How this section is made
Each figure is the median across the 11 grid cells holding the 42 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 1057:1226 (37.125, -118.675). 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 11 distinct grid cells holding 42 of the 42 in-range records; extremes and elevation at the typical cell 1057:1226 (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 37.00_-118.750, lapse-corrected +1125 m at 6.5 °C/km. Elevation: ETOPO 2022, 3650 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.
NativeCalifornia, Nevada · 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 marker37.634, -118.256 · in the densest population, 47 records (89% of those in range)
Kew's description“temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 53 georeferenced records inside the native range; the climate across the range on the 42 of them placed to within 10 km; the map shows only the 17 openly licensed ones, which alone would put the marker in the same place. 11 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 53 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 chartaceum, photograph 1did not loadPolemonium chartaceum, photograph 2did not loadPolemonium chartaceum, photograph 3did not loadPolemonium chartaceum, photograph 4did not loadPolemonium chartaceum, photograph 5did not loadPolemonium chartaceum, photograph 6did not load

Photographs: (c) Trevor Van Loon, some rights reserved (CC BY) (6).

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

Draba densifolia Draba densifolia Dense-leaved draba Photo: CC BY, glittergravelEricameria suffruticosa Ericameria suffruticosa Singlehead goldenbush Photo: CC BY, justanotherbirdbrainRibes montigenum Ribes montigenum Grossulariaceae Photo: CC BY, Daughter DadCarex tahoensis Carex tahoensis Tahoe sedge Photo: CC BY, Matt BergerVeronica utahensis Veronica utahensis Plantaginaceae Photo: CC0, Walter FertigDraba sphaeroides Draba sphaeroides Ball draba Photo: CC BY, Matt Lavin

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 Satekov 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 confertum var. chartaceum; Polemonium viscosum subsp. chartaceum; Polemonium viscosum var. chartaceum. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Polemoniaceae
Described by
H.Mason
Native to
California, Nevada
Wild records
53 in range · 17 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 37.00_-118.750, lapse-corrected +1125 m at 6.5 °C/km; read, and set aside: the correction for elevation, +1125 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's, so no cold floor is shown
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 2026-10-22none of the photographs on this page is credited to GBIF: those shown are other sources', and GBIF's were the same photographs or were set aside by the photograph rules
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 17 datasets via GBIF.org; each carries its own licence.

Cultifolio

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