Asclepias fascicularis Decne.
Mexican milkweed, Mexican whorled milkweed, Mexican whorled milkweed, Narrow-leaf milkweed
Every figure on this page is derived from public data by a stated rule and says its source; nothing here is written by a person or a model, except the Wikipedia passage, which is quoted and marked as such. How it is made.
Summary
Asclepias fascicularis is a species of milkweed known by the common names narrowleaf milkweed and Mexican whorled milkweed. It is a perennial herb that grows in a variety of habitats.
Text from Wikipedia, “Asclepias fascicularis”, CC BY-SA 4.0, quoted as written. Kept separate from everything derived here.
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 ›
The opening of Wikipedia, “Asclepias”, CC BY-SA 4.0, quoted as written.
At a glance
Also known as Asclepias fasciculata Hemsl.; Asclepias macrophylla var. comosa Durand & Hilg.
Cultivation
Its year Rain rule: a winter growing season, December to March in the northern hemisphere (December to March at the habitat, northern).
This species’ habitat figures, and what two fixed rules read from them.
The rain rule reads a winter growing season: 70% of the year's rain (345 mm of 488 mm) falls in December to March, cooler than the year (wet-season mean 9.9 °C against a yearly mean of 15.1 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: June to September.
Read from the median year of CHELSA monthly rainfall and mean temperature across the envelope cells: 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 gives a season to reverse. A reading of the curves, not an observation of the plant.
Rain Habitat rain 488 mm a year, wettest January at 96 mm, driest July at 1 mm (habitat calendar, northern hemisphere).
This species’ habitat figures, with their source.
488 mm a year at the habitat, 345 mm of it December to March. Wettest month January at 96 mm, driest July at 1 mm; 3 months under 5 mm. Across the envelope cells the year's total runs 297 mm to 978 mm (10th to 90th percentile of each cell's own year) (median year across the envelope cells, CHELSA; habitat calendar, northern hemisphere).
CHELSA monthly precipitation, median year across the envelope cells. The rain that falls where the species is recorded; nothing about how the plant takes water.
Light Open sky over the habitat: 15 to 52 mol/m²/day.
This species’ habitat figures, with their source.
Open sky over the habitat: 15 to 52 mol/m²/day across the year (daily light integral, median year across the envelope cells, CHELSA; the lowest 10th-percentile month across the cells is 11, the highest 90th-percentile month 54).
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.
Warmth and air Cold floor -0.7 °C (1st-percentile habitat night, NASA POWER).
This species’ habitat figures, with their source.
Coldest: the 1st-percentile night over 44 years at the typical cell is -0.7 °C, the absolute minimum -5.9 °C, about 6 frost nights a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 42.7 °C. Monthly means: coldest night 4.1 °C in January (across the envelope cells -4.5 °C to 7.7 °C), warmest day 30.0 °C in July (median year across the envelope cells, CHELSA). Cold floor: -0.7 °C, which is the 1st-percentile night over 44 years at the typical cell (NASA POWER).
NASA POWER daily minima and maxima 1981–2024 at the typical cell, lapse-corrected to its elevation; CHELSA monthly means, median year across the envelope cells, CHELSA. The cold floor is the figure named in its sentence. Not a measured survival limit for any plant in a pot.
Relative humidity at the habitat: 50 to 59% across the year (monthly means, median year across the envelope cells, CHELSA). A figure about the air, saying nothing about how the plant takes water.
CHELSA relative humidity, median year across the envelope cells.
The figures the cards read from are in Climate below, and where they came from in Natural habitat.
Climate across the habitat
Figures by month
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Day °C | 14 / 5–18 | 15 / 6–18 | 17 / 10–20 | 20 / 14–23 | 23 / 19–27 | 27 / 22–32 | 30 / 25–34 | 30 / 25–34 | 27 / 24–31 | 23 / 18–26 | 18 / 9–21 | 14 / 4–17 |
| Night °C | 4 / -5–8 | 5 / -4–8 | 6 / -1–9 | 8 / 2–11 | 10 / 6–13 | 13 / 10–16 | 16 / 13–18 | 16 / 13–18 | 14 / 11–17 | 11 / 5–14 | 7 / -0–11 | 4 / -5–8 |
| Rain mm | 96 / 48–182 | 95 / 44–166 | 72 / 39–137 | 34 / 20–72 | 15 / 6–47 | 4 / 2–22 | 1 / 0–11 | 2 / 1–12 | 7 / 5–19 | 26 / 16–58 | 54 / 29–127 | 82 / 43–189 |
| DLI | 17 / 13–21 | 23 / 19–27 | 32 / 29–36 | 42 / 38–45 | 48 / 45–51 | 52 / 50–54 | 52 / 50–53 | 47 / 45–48 | 39 / 36–41 | 29 / 25–32 | 19 / 15–24 | 15 / 11–20 |
| RH % | 58 / 51–64 | 59 / 53–62 | 58 / 53–62 | 55 / 50–60 | 54 / 47–62 | 52 / 43–62 | 50 / 41–61 | 50 / 42–61 | 51 / 43–61 | 53 / 47–60 | 56 / 49–61 | 58 / 50–63 |
Each figure is the median across the 970 grid cells holding the 1686 in-range records, with the 10th–90th percentile span across those cells after the slash where it differs. Extremes and elevation were read at the typical cell 1026:1176 (38.675, -121.175). Over 44 years there: absolute minimum -5.9 °C, 1st-percentile night -0.7 °C, 99th-percentile day 42.7 °C. Normals: CHELSA V2.1 1981–2010 climatology, 0.05° cells (each the mean of ~36 1 km pixels). Envelope: median and 10th–90th percentile of each month across the 970 distinct grid cells holding the 1686 in-range records; extremes and elevation at the typical cell 1026:1176 (its coldest month's mean night nearest the median across cells); its position is the cell centre. Extremes: NASA POWER (MERRA-2) daily 1981–2024, cell 38.50_-121.250, lapse-corrected -49 m at 6.5 °C/km. Elevation: ETOPO 2022, 79 m (cell mean).
Natural habitat
Photographs
Photographs: (c) LJ Moore-McClelland, some rights reserved (CC BY) (4); no rights reserved · CC0; (c) Matt Berger, some rights reserved (CC BY) (3).
Photographs: iNaturalist and Wikimedia Commons did not answer when this page was built; what is shown came from the sources that did.
Papers naming this species
Works whose title or abstract names Asclepias fascicularis, most cited first, from OpenAlex (CC0). A mention, not a cultivation source: nothing on this page is drawn from them.
Related
Similar habitat climate the 6 species whose habitat climate is nearest this one's: mean day and night, month by month, and rain on a log scale, in calendar order, so a habitat with the same seasons six months out is far, not near. Nothing else counts: not range, not family.
Collinsia heterophylla Chinese-houses
Clarkia unguiculata Clarkia
Nemophila menziesii Baby Blue Eyes
Clarkia purpurea purple clarkia
Penstemon heterophyllus bunchleaf penstemon
Heteromeles arbutifolia California HollyOther Asclepias 10 in the reference
Asclepias curassavica Bloodflower
Asclepias incarnata Pleurisy Root
Asclepias perennis Shore Milkweed
Asclepias purpurascens purple milkweed
Asclepias speciosa Greek milkweed
Asclepias subulata rush milkweed
Asclepias syriaca Broadleaf Milkweed
Asclepias tuberosa Butterfly Milkweed
Asclepias verticillata eastern whorled milkweed
Asclepias viridis antelope-horns History & registers
Where this page came from built 2026-09-20 · dossier v2 · node
gbif.species answeredcarried from build of 2026-09-20 (offline re-derivation; the backbone was not asked)gbif.synonyms answeredcarried from build of 2026-09-20 (offline re-derivation; the backbone was not asked)gbif.vernacular answeredcarried from build of 2026-09-20 (offline re-derivation; the backbone was not asked)wcvp.distribution answeredgbif.occurrences answeredGBIF occurrence download https://doi.org/10.15468/dl.3h4zamclimate answeredwikidata answeredcarried from build of 2026-09-20 (rederive); that build: carried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)wikipedia answeredcarried from build of 2026-09-20; this build: skippedinat.taxon not askedcarried from build of 2026-09-20 (rederive)inat.photos.wild answeredcarried from build of 2026-09-20; this build: skippedinat.photos.cultivated nothing to reportcarried from build of 2026-09-20 (rederive); that build: carried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)commons not askedcarried from build of 2026-09-20 (rederive); that build: carried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)gbif.media answeredopenalex answeredcarried from build of 2026-09-20; this build: skippedEvery upstream is recorded as having answered, reported nothing, or refused. Only “nothing to report” is ever shown as an absence. Records came from 57 datasets via GBIF.org; each carries its own licence.








