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An example collection, so you can see what this page does. Nothing added here is kept: leaving deletes it.
Asclepias quadrifolia; photograph (c) paulconstantino, some rights reserved (CC BY) CC BY(c) paulconstantino, some rights reserved (CC BY) · observed growing wild · 2026-06-21

Asclepias quadrifolia Jacq.

Four-leaf milkweed; Whorled milkweed; Four-leaved milkweed

Apocynaceae · Ontario, Illinois +26

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Asclepias quadrifolia, photograph (c) Tom Norton, some rights reserved (CC BY)Asclepias quadrifolia, photograph (c) Tom Norton, some rights reserved (CC BY)Asclepias quadrifolia, photograph (c) Erin Collins, some rights reserved (CC BY)Asclepias quadrifolia, photograph author not stated, no rights reservedAsclepias quadrifolia, photograph author not stated, no rights reservedAsclepias quadrifolia, photograph author not stated, no rights reserved 74 photographs ›
Habitat figures
Cold floor (1 night in 100)
-14.0°C
Record low -27.5 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
29°C
Jul at the habitat CHELSA
Rain a year (median across the range)
1,215mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
13–40DLI
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

Asclepias quadrifolia, commonly called four-leaved milkweed or fourleaf milkweed, is a species of milkweed in the Apocynaceae (dogbane) family. It is sometimes referred to as whorled milkweed, but it should not be confused with Asclepias verticillata. A. quadrifolia occurs in the eastern United States and Canada.

Quoted from Wikipedia, "Asclepias quadrifolia", CC BY-SA 4.0.

About the genus · Asclepias

Asclepias is a genus of herbaceous, perennial, flowering plants known as milkweeds, named for their latex, a milky substance containing cardiac glycosides termed cardenolides, exuded where cells are damaged. Most species are toxic to humans and many other species, primarily due to the presence of cardenolides. However, as with many such plants, some species feed upon milkweed leaves or the nectar from their flowers. More on Wikipedia ›

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

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (861 mm of 1,209 mm) takes 8 months, March to September and November. Mean temperature moves 24.0 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to March and May.

Rain

1,209 mm in the median year at the habitat, 861 mm of it March to September and November. Wettest month May at 124 mm, driest month February at 79 mm. Across the grid cells of the range the year's total runs 1,036 mm to 1,473 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,215 mm, is the year's rain at the top of the page; the 1,209 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: 13 to 40 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 10, 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 -14.0 °C, the absolute minimum -27.5 °C, 5,324 frost nights in 44 years, 121.0 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 34.8 °C. Monthly means: the coldest month's mean nightly low -3.5 °C in January (across the grid cells of the range -7.0 °C to -0.4 °C), the warmest month's mean daily high 29.1 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -14.0 °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 59% 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 +198 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 Asclepias quadrifolia through the yearWarmest month July, mean daily high 29 °C; coldest month January, mean nightly low -3.5 °C; 1,209 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°-20°0°20°40°frost34.8° 99th-percentile day, NASA POWER-27.5° lowest night in 44 years, NASA POWER°C · day and nightcold quarter050100150200mm rainDLI 13–40RH 56–59%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 995 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 °C5 / 1–98 / 4–1113 / 8–1618 / 15–2123 / 20–2527 / 24–2929 / 26–3228 / 26–3125 / 22–2719 / 16–2113 / 10–157 / 3–10
Night °C-4 / -7–0-2 / -6–12 / -2–57 / 4–1012 / 9–1517 / 14–2020 / 17–2219 / 16–2115 / 13–179 / 7–124 / 2–6-2 / -4–1
Rain mm82 / 61–12879 / 61–133102 / 82–132109 / 89–129124 / 101–153114 / 98–135114 / 96–14196 / 82–117103 / 82–12493 / 72–12199 / 80–12994 / 73–137
DLI15 / 13–1720 / 18–2127 / 25–2834 / 32–3537 / 36–3840 / 38–4138 / 37–4135 / 33–3829 / 27–3122 / 20–2415 / 13–1713 / 10–15
RH %58 / 57–6057 / 56–5856 / 55–5756 / 55–5758 / 57–6059 / 58–6159 / 58–6259 / 57–6259 / 57–6158 / 56–6058 / 57–6059 / 57–60
How this section is made
Each figure is the median across the 995 grid cells holding the 1407 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 1049:2008 (37.525, -79.575). Over 44 years there: absolute minimum -27.5 °C, 1st-percentile night -14.0 °C, 99th-percentile day 34.8 °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 995 distinct grid cells holding 1407 of the 1407 in-range records; extremes and elevation at the typical cell 1049:2008 (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 37.50_-79.375, lapse-corrected +198 m at 6.5 °C/km. Elevation: ETOPO 2022, 561 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.
NativeOntario, Illinois, Iowa, Kansas, Missouri, Oklahoma, Connecticut, Indiana, Massachusetts, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Alabama, Arkansas, Georgia, Kentucky, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, District of Columbia · introduced: Germany · 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 marker39.635, -78.318 · in the densest population, 946 records (52% of those in range)
Extinct inDelaware · recorded as extinct by WCVP: history, not habitat; no records are tested against these regions
Kew's description“perennial” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 1805 georeferenced records inside the native range; the climate across the range on the 1407 of them placed to within 10 km; the map shows only the 493 openly licensed ones, which alone would put the marker 815 km away. 398 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 1805 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Asclepias quadrifolia, photograph 1did not loadAsclepias quadrifolia, photograph 2did not loadAsclepias quadrifolia, photograph 3did not loadAsclepias quadrifolia, photograph 4did not loadAsclepias quadrifolia, photograph 5did not loadAsclepias quadrifolia, photograph 6did not load

Photographs: (c) Tom Norton, some rights reserved (CC BY) (2); (c) Erin Collins, 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.

Aplectrum hyemale Aplectrum hyemale Puttyroot Photo: CC0, author not statedHypoxis hirsuta Hypoxis hirsuta Yellow star-grass Photo: CC BY, Brandon CorderDioscorea villosa Dioscorea villosa Wild yam Photo: CC0, author not statedViola pedata Viola pedata Bird-foot violet Photo: CC BY, Patrick CominsThaspium trifoliatum Thaspium trifoliatum Purple meadow-parsnip Photo: CC BY, Daniel BeeversArnoglossum reniforme Arnoglossum reniforme Great Indian plantain Photo: CC BY, Jesse

Other Asclepias 48 in the reference

Asclepias albicans Asclepias albicans White-Stem milkweed Photo: CC BY, Matt BergerAsclepias amplexicaulis Asclepias amplexicaulis Blunt-leaf milkweed Photo: CC0, author not statedAsclepias angustifolia Asclepias angustifolia Arizona milkweed Photo: CC BY, Cheng-Te HsuAsclepias asperula Asclepias asperula Antelope horns Photo: CC BY, Parker James LloydAsclepias brachystephana Asclepias brachystephana Shortcrown milkweed Photo: CC BY, Cody HinchliffAsclepias californica Asclepias californica California milkweed Photo: CC BY, klickloAsclepias cordifolia Asclepias cordifolia Purple milkweed Photo: CC BY-SA, Brian FinzelAsclepias cryptoceras Asclepias cryptoceras Humboldt Mountains milkweed Photo: CC BY, Parker James LloydAsclepias curassavica Asclepias curassavica Bloodflower Photo: CC BY, Ricard Busquets ReverteAsclepias engelmanniana Asclepias engelmanniana Engelmann's milkweed Photo: CC BY, Rajan RaoAsclepias eriocarpa Asclepias eriocarpa Indian milkweed Photo: CC BY, klickloAsclepias erosa Asclepias erosa Desert milkweed Photo: CC BY, CK2AZ all 49 ›

Names & registers

Also known as Asclepias quadrifolia var. lanceolata; Asclepias quadrifolia var. oppositifolia; Asclepias vanilla. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Apocynaceae
Described by
Jacq.
Native to
Ontario, Illinois, Iowa +25
Wild records
1805 in range · 493 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; 18 records within 1 km of a botanic garden, herbarium or zoo left out (17 at a botanic garden or arboretum, 1 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 37.50_-79.375, lapse-corrected +198 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 65 datasets via GBIF.org; each carries its own licence.

Cultifolio

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