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Ambrosia chenopodiifolia; photograph (c) Jose Luis Leon de la Luz, some rights reserved (CC BY) CC BY(c) Jose Luis Leon de la Luz, some rights reserved (CC BY) · observed growing wild · 2026-05-19

Ambrosia chenopodiifolia (Benth.) W.W.Payne

San Diego bursage; San Diego burr ragweed; San Diego bur ragweed

Asteraceae · California, Mexico Northwest

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Ambrosia chenopodiifolia, photograph (c) Sula Vanderplank, some rights reserved (CC BY)Ambrosia chenopodiifolia, photograph (c) Sula Vanderplank, some rights reserved (CC BY)Ambrosia chenopodiifolia, photograph (c) Sula Vanderplank, some rights reserved (CC BY)Ambrosia chenopodiifolia, photograph (c) Ian McFaul, some rights reserved (CC BY)Ambrosia chenopodiifolia, photograph (c) Ian McFaul, some rights reserved (CC BY)Ambrosia chenopodiifolia, photograph (c) Ian McFaul, some rights reserved (CC BY) 75 photographs ›
Habitat figures
Cold floor (1 night in 100)
6.4°C
Record low 2.7 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
27°C
Aug and Sep at the habitat CHELSA
Rain a year (median across the range)
144mm
2 months of 25 mm or more in the median year CHELSA
Open-sky light
23–52DLI
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 March, read as a winter growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Ambrosia chenopodiifolia is a species of ragweed known by the common names San Diego bursage and San Diego bur ragweed. It is native to the Mexican states of Baja California and Baja California Sur (Comondu Municipality), as well as to Orange and San Diego Counties it int US State of California. It is a member of the coastal sage scrub plant community.

Quoted from Wikipedia, "Ambrosia chenopodiifolia", CC BY-SA 4.0.

About the genus · Ambrosia

In the ancient Greek myths, ambrosia is the food or drink of the Greek gods, and is often depicted as conferring longevity or immortality upon whoever consumed it. It was brought to the gods in Olympus by doves and served either by Hebe or by Ganymede at the heavenly feast.

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

Cultivation

Seasons

The rain rule reads a winter growing season: 70% of the median year's rain (112 mm of 142 mm) falls in November to March, cooler than the year (wet-season mean 14.8 °C against a yearly mean of 17.8 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: May to September.

Rain

142 mm in the median year at the habitat, 112 mm of it November to March. Wettest month February at 27 mm, driest month June at 1 mm; 4 months under 5 mm. Across the grid cells of the range the year's total runs 81 mm to 278 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 144 mm, is the year's rain at the top of the page; the 142 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: 23 to 52 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 21, the highest 90th-percentile month 54).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is 6.4 °C, the absolute minimum 2.7 °C, no frost in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 39.9 °C. Monthly means: the coldest month's mean nightly low 10.6 °C in January (across the grid cells of the range 7.8 °C to 13.6 °C), the warmest month's mean daily high 26.9 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: 6.4 °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 60% 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 -121 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 Ambrosia chenopodiifolia through the yearWarmest months August and September, mean daily high 27 °C; coldest month January, mean nightly low 10.6 °C; 142 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.0°10°20°30°40°50°39.9° 99th-percentile day, NASA POWER2.7° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0102030405060mm rainDLI 23–52RH 53–60%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 256 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 °C18 / 17–2018 / 16–2119 / 17–2320 / 17–2621 / 18–2823 / 19–3226 / 21–3527 / 22–3527 / 23–3324 / 21–2821 / 19–2418 / 17–21
Night °C11 / 8–1411 / 8–1411 / 9–1413 / 11–1414 / 13–1616 / 15–1719 / 18–2120 / 19–2219 / 18–2116 / 15–1913 / 11–1711 / 8–14
Rain mm23 / 12–4927 / 10–6023 / 7–535 / 2–192 / 0–31 / 0–23 / 1–74 / 2–147 / 4–168 / 7–1414 / 6–2625 / 17–41
DLI25 / 23–2731 / 28–3339 / 37–4147 / 45–4950 / 49–5352 / 50–5449 / 48–5046 / 45–4741 / 40–4234 / 32–3627 / 25–2823 / 21–24
RH %54 / 49–5955 / 49–6157 / 48–6358 / 46–6460 / 47–6760 / 44–7059 / 45–7159 / 47–7058 / 48–6757 / 48–6454 / 48–6053 / 50–59
How this section is made
Each figure is the median across the 256 grid cells on land that hold in-range records (728 records in those cells; 3 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 1226:1320 (28.675, -113.975). Over 44 years there: absolute minimum 2.7 °C, 1st-percentile night 6.4 °C, 99th-percentile day 39.9 °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 256 distinct grid cells holding 728 of the 732 in-range records (3 further cells with records at sea, by the elevation layer, left out); extremes and elevation at the typical cell 1226:1320 (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 28.50_-113.750, lapse-corrected -121 m at 6.5 °C/km. Elevation: ETOPO 2022, 200 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, Mexico Northwest · 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 marker31.693, -116.617 · in the densest population, 669 records (72% of those in range)
Kew's description“subtropical” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 926 georeferenced records inside the native range; the climate across the range on the 728 of them in the land cells it reads, of 732 placed to within 10 km; the map shows only the 477 openly licensed ones, which alone would put the marker 6 km away. 41 records outside the WCVP native range not used. 194 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 926 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Ambrosia chenopodiifolia, photograph 1did not loadAmbrosia chenopodiifolia, photograph 2did not loadAmbrosia chenopodiifolia, photograph 3did not loadAmbrosia chenopodiifolia, photograph 4did not loadAmbrosia chenopodiifolia, photograph 5did not loadAmbrosia chenopodiifolia, photograph 6did not load

Photographs: (c) Sula Vanderplank, some rights reserved (CC BY) (3); (c) Ian McFaul, some rights reserved (CC BY) (3).

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

Euphorbia misera Euphorbia misera Cliff spurge Photo: CC BY, Sula VanderplankEchinocereus maritimus Echinocereus maritimus Cactaceae Photo: CC BY-SA, Michelle Cloud-HughesGambelia juncea Gambelia juncea Baja Bush Snapdragon Photo: CC BY, Marc WhitakerMyrtillocactus cochal Myrtillocactus cochal Baja California Candelabra Cactus Photo: CC BY, Jose Luis Leon de la LuzAcanthogilia gloriosa Acanthogilia gloriosa Baja Phlox Photo: CC BY, Jose Luis Leon de la LuzAgave shawii Agave shawii Shaw's agave Photo: CC BY, Diego Maldonado de la Torre

Other Ambrosia 19 in the reference

Ambrosia acanthicarpa Ambrosia acanthicarpa Annual bursage Photo: CC BY, Anders HastingsAmbrosia ambrosioides Ambrosia ambrosioides Big bursage Photo: CC BY, Bruce HartmanAmbrosia arborescens Ambrosia arborescens Asteraceae Photo: CC BY, Efrain FreireAmbrosia artemisiifolia Ambrosia artemisiifolia Ragweed Photo: CC BY, Bobo-XAmbrosia bryantii Ambrosia bryantii Asteraceae Photo: CC BY, Juan Cruzado CortésAmbrosia chamissonis Ambrosia chamissonis Beachbur Photo: CC0, author not statedAmbrosia cheiranthifolia Ambrosia cheiranthifolia South Texas ambrosia Photo: CC BY, Eric KnightAmbrosia confertiflora Ambrosia confertiflora Weakleaf burr ragweed Photo: CC BY, CK2AZAmbrosia cordifolia Ambrosia cordifolia Tucson burr ragweed Photo: CC0, author not statedAmbrosia deltoidea Ambrosia deltoidea Triangle bursage Photo: CC BY, Matt BergerAmbrosia dumosa Ambrosia dumosa White bur-sage Photo: CC BY, CK2AZAmbrosia hispida Ambrosia hispida Coastal ragweed Photo: CC BY, Alexis López Hernández all 20 ›

Names & registers

Also known as Franseria chenopodiifolia; Franseria lancifolia; Gaertnera chenopodiifolia; Gaertneria chenopodiifolia. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Asteraceae
Described by
(Benth.) W.W.Payne
Native to
California, Mexico Northwest
Wild records
926 in range · 477 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 28.50_-113.750, lapse-corrected -121 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 34 datasets via GBIF.org; each carries its own licence.

Cultifolio

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