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An example collection, so you can see what this page does. Nothing added here is kept: leaving deletes it.
Caltha leptosepala; photograph (c) Caleb Catto, some rights reserved (CC BY) CC BY(c) Caleb Catto, some rights reserved (CC BY) · observed growing wild · 2026-08-10

Caltha leptosepala DC.

Slender-sepal marsh marigold; Elkslip marsh marigold; White marsh marigold; Elkslip

Ranunculaceae · Alaska, Yukon +8

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Caltha leptosepala, photograph (c) Alan Covington, some rights reserved (CC BY)Caltha leptosepala, photograph (c) Caleb Catto, some rights reserved (CC BY)Caltha leptosepala, photograph (c) i like lizards, some rights reserved (CC BY)Caltha leptosepala, photograph author not stated, no rights reservedCaltha leptosepala, photograph author not stated, no rights reservedCaltha leptosepala, photograph author not stated, no rights reserved 77 photographs ›
Habitat figures
Cold floor (1 night in 100)
-21.3°C
Record low -29.6 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
19°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,477mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
7–44DLI
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 October to April, 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

Caltha leptosepala, the white marsh marigold, twinflowered marsh marigold, or broadleaved marsh marigold, is a North American species of flowering plant in the buttercup family. The species has regionally distinct variations.

Quoted from Wikipedia, "Caltha leptosepala", CC BY-SA 4.0.

About the genus · Caltha

Caltha is a genus of rhizomatous perennial flowering plants in the family Ranunculaceae, to which ten species have been assigned. They occur in moist environments in temperate and cold regions of both the Northern and Southern Hemispheres. Their leaves are generally heart-shaped or kidney-shaped, or are characteristically diplophyllous. More on Wikipedia ›

Quoted from Wikipedia, "Caltha", 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 (1,116 mm of 1,482 mm) falls in October to April, the cooler part of the year, but the mean nightly low is below freezing in February, March, April, May, November, 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: April to October.

Rain

1,482 mm in the median year at the habitat, 1,116 mm of it October to April. Wettest month January at 214 mm, driest month July at 55 mm. Across the grid cells of the range the year's total runs 791 mm to 3,259 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,477 mm, is the year's rain at the top of the page; the 1,482 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 44 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 2, the highest 90th-percentile month 53).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -21.3 °C, the absolute minimum -29.6 °C, 10,313 frost nights in 44 years, 234.4 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 26.2 °C. Monthly means: the coldest month's mean nightly low -9.9 °C in December (across the grid cells of the range -17.7 °C to -4.2 °C), the warmest month's mean daily high 19.3 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: -21.3 °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: 53 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 +401 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 Caltha leptosepala through the yearWarmest months July and August, mean daily high 19 °C; coldest month December, mean nightly low -9.9 °C; 1,482 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°30°frost26.2° 99th-percentile day, NASA POWER-29.6° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400500mm rainDLI 7–44RH 53–63%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 488 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 / -10–2-1 / -8–31 / -4–65 / 0–910 / 5–1415 / 11–2019 / 14–2519 / 14–2415 / 9–208 / 1–141 / -7–6-3 / -11–2
Night °C-9 / -17–-4-9 / -16–-4-7 / -13–-3-5 / -9–-1-1 / -5–33 / 0–77 / 4–107 / 4–103 / -1–7-2 / -7–3-7 / -14–-2-10 / -18–-4
Rain mm214 / 61–423157 / 47–301141 / 49–29099 / 49–22189 / 53–17292 / 26–15655 / 12–13856 / 12–14474 / 25–182106 / 58–358187 / 68–474212 / 62–422
DLI9 / 4–1615 / 8–2324 / 18–3334 / 28–4241 / 34–4842 / 35–5344 / 32–5339 / 25–4829 / 17–3918 / 9–2810 / 4–187 / 2–14
RH %62 / 54–6861 / 56–6561 / 57–6559 / 55–6358 / 51–6357 / 47–6353 / 42–6353 / 42–6454 / 45–6459 / 49–6663 / 53–6962 / 54–68
How this section is made
Each figure is the median across the 488 grid cells holding the 804 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 1056:1221 (37.175, -118.925). Over 44 years there: absolute minimum -29.6 °C, 1st-percentile night -21.3 °C, 99th-percentile day 26.2 °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 488 distinct grid cells holding 804 of the 804 in-range records; extremes and elevation at the typical cell 1056:1221 (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 +401 m at 6.5 °C/km. Elevation: ETOPO 2022, 2926 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.
NativeAlaska, Yukon, Alberta, British Columbia, Idaho, Montana, Oregon, Washington, Arizona, California · 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 marker46.853, -121.76 · in the densest population, 546 records (56% 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 976 georeferenced records inside the native range; the climate across the range on the 804 of them placed to within 10 km; the map shows only the 370 openly licensed ones, which alone would put the marker 528 km away. 822 records outside the WCVP native range not used. 172 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 976 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Caltha leptosepala, photograph 1did not loadCaltha leptosepala, photograph 2did not loadCaltha leptosepala, photograph 3did not loadCaltha leptosepala, photograph 4did not loadCaltha leptosepala, photograph 5did not loadCaltha leptosepala, photograph 6did not load

Photographs: (c) Alan Covington, some rights reserved (CC BY); (c) Caleb Catto, some rights reserved (CC BY); (c) i like lizards, some rights reserved (CC BY); author not stated, no rights reserved · CC0 (3).

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

Kalmia microphylla Kalmia microphylla Alpine bog laurel Photo: CC BY, Matt BergerAthyrium americanum Athyrium americanum Alpine ladyfern Photo: CC BY, James H. ThomasPhyllodoce empetriformis Phyllodoce empetriformis Pink mountain heather Photo: CC BY-SA, Nick T.Erythranthe lewisii Erythranthe lewisii Lewis' monkeyflower Photo: CC0, Ben KeenPotentilla flabellifolia Potentilla flabellifolia Fan-leaved cinquefoil Photo: CC0, author not statedGentiana calycosa Gentiana calycosa Mountain bog gentian Photo: CC0, author not stated

Other Caltha 5 in the reference

Caltha alba Caltha alba White Marsh Marigold Photo: CC BY, Sindhu HaridasCaltha biflora Caltha biflora Broad-leaved marsh marigold Photo: CC0, author not statedCaltha obtusa Caltha obtusa White Caltha Photo: CC BY-SA, Jacob LittlejohnCaltha palustris Caltha palustris Marsh marigold Photo: CC BY, Eugene PopovCaltha sagittata Caltha sagittata Arrow-leaved Marigold Photo: CC BY, Yuri Sofronov

Names & registers

Also known as Caltha auriculata; Caltha biflora var. howellii; Caltha biflora var. rotundifolia; Caltha chelidonii; Caltha howelliae and 15 more. (GBIF Backbone)

Kew accepts as species of their own Caltha chionophila: 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)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Ranunculaceae
Described by
DC.
Native to
Alaska, Yukon, Alberta +7
Wild records
976 in range · 370 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; 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 2026-10-21
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-21NASA POWER (MERRA-2) daily 1981–2024, cell 37.00_-118.750, lapse-corrected +401 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 85 datasets via GBIF.org; each carries its own licence.

Cultifolio

Opening your plants…