Romneya trichocalyx Eastw.
Bristly Matilija poppy, Hairy Matilija Poppy, bristly Matilija poppy, hairy matilija-poppy
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
Romneya trichocalyx, the bristly Matilija poppy or hairy Matilija poppy, is a species of flowering plant in the poppy family. This poppy is native to San Diego, Ventura, and Santa Barbara counties in California, as well as Baja California, Mexico, where it grows in dry canyons in chaparral and coastal sage scrub plant communities. Like its relative Romneya coulteri, it is used as an ornamental plant, kept for its large, showy flowers.
Text from Wikipedia, “Romneya trichocalyx”, CC BY-SA 4.0, quoted as written. Kept separate from everything derived here.
About the genus · Romneya
Romneya is a genus of flowering plants belonging to the poppy family (Papaveraceae). There are two species in the genus Romneya, which was named after the Irish astronomer John Thomas Romney Robinson; the first discovered species R. coulteri commemorates Romney Robinson's close friendship with the Irish botanist Thomas Coulter. They are known commonly as Matilija poppies, bush poppies, California poppies, or tree poppies. More on Wikipedia ›
The opening of Wikipedia, “Romneya”, CC BY-SA 4.0, quoted as written.
At a glance
Also known as Romneya coulteri var. trichocalyx (Eastw.) Jeps.
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 (257 mm of 351 mm) falls in December to March, cooler than the year (wet-season mean 12.4 °C against a yearly mean of 16.5 °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 351 mm a year, wettest February at 79 mm, driest June at 2 mm (habitat calendar, northern hemisphere).
This species’ habitat figures, with their source.
351 mm a year at the habitat, 257 mm of it December to March. Wettest month February at 79 mm, driest June at 2 mm; 3 months under 5 mm. Across the envelope cells the year's total runs 282 mm to 546 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: 20 to 52 mol/m²/day.
This species’ habitat figures, with their source.
Open sky over the habitat: 20 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 18, 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 4.3 °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 4.3 °C, the absolute minimum -0.7 °C, 2 frost nights in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 35.5 °C. Monthly means: coldest night 7.0 °C in January (across the envelope cells 2.8 °C to 9.6 °C), warmest day 28.3 °C in August (median year across the envelope cells, CHELSA). Cold floor: 4.3 °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: 52 to 58% 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 | 17 / 14–18 | 17 / 14–18 | 18 / 16–20 | 20 / 18–22 | 22 / 19–25 | 25 / 21–28 | 28 / 23–31 | 28 / 24–31 | 27 / 24–30 | 23 / 21–26 | 20 / 17–21 | 17 / 14–18 |
| Night °C | 7 / 3–10 | 8 / 3–10 | 9 / 4–11 | 10 / 6–12 | 12 / 10–14 | 15 / 13–16 | 18 / 15–19 | 18 / 15–19 | 17 / 14–18 | 14 / 10–16 | 10 / 6–13 | 7 / 3–10 |
| Rain mm | 64 / 48–114 | 79 / 56–120 | 62 / 49–86 | 25 / 16–39 | 6 / 3–11 | 2 / 1–3 | 2 / 1–9 | 2 / 1–11 | 6 / 4–10 | 18 / 13–26 | 33 / 25–49 | 52 / 39–85 |
| DLI | 22 / 19–24 | 26 / 25–29 | 35 / 34–38 | 44 / 43–46 | 50 / 48–52 | 52 / 51–54 | 51 / 49–52 | 47 / 45–48 | 40 / 39–41 | 31 / 30–33 | 24 / 22–26 | 20 / 18–22 |
| RH % | 53 / 50–59 | 56 / 53–60 | 58 / 53–62 | 57 / 50–61 | 58 / 49–64 | 57 / 47–64 | 56 / 46–65 | 55 / 46–64 | 55 / 47–64 | 54 / 48–61 | 52 / 48–59 | 52 / 50–58 |
Each figure is the median across the 324 grid cells holding the 918 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 1151:1266 (32.425, -116.675). Over 44 years there: absolute minimum -0.7 °C, 1st-percentile night 4.3 °C, 99th-percentile day 35.5 °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 324 distinct grid cells holding the 918 in-range records; extremes and elevation at the typical cell 1151:1266 (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 32.50_-116.875, lapse-corrected -58 m at 6.5 °C/km. Elevation: ETOPO 2022, 336 m (cell mean).
Natural habitat
Photographs
Photographs: (c) Millie Basden, some rights reserved (CC BY); no rights reserved · CC0 (5); (c) George Williams, some rights reserved (CC BY) (2).
Photographs: iNaturalist 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 Romneya trichocalyx, 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.
Crassula solieri Little Pygmyweed
Diplacus puniceus Red Sticky Monkeyflower
Dudleya edulis Ladies Fingers
Dudleya viscida Sticky Dudleya
Dudleya pulverulenta chalk dudleya
Salvia clevelandii Cleveland SageOther Romneya 1 in the reference
History & registers
Where this page came from built 2026-09-20 · dossier v2 · node
gbif.species answeredcarried from build of 2026-09-19 (offline re-derivation; the backbone was not asked)gbif.synonyms answeredcarried from build of 2026-09-19 (offline re-derivation; the backbone was not asked)gbif.vernacular answeredcarried from build of 2026-09-19 (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 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)wikipedia answeredcarried from build of 2026-09-19; this build: skippedinat.taxon not askedinat.photos.wild answeredcarried from build of 2026-09-19; this build: skippedinat.photos.cultivated nothing to reportcarried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)commons nothing to reportcarried from build of 2026-09-19 (rederive); that build: carried from build of 2026-09-19 (rederive)gbif.media answeredopenalex answeredcarried from build of 2026-09-19; 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 36 datasets via GBIF.org; each carries its own licence.