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Ruellia drummondiana; photograph (c) James Todd McCann, some rights reserved (CC BY) CC BY(c) James Todd McCann, some rights reserved (CC BY) · observed growing wild · 2026-08-20

Ruellia drummondiana (Nees) A.Gray

Drummond's ruellia; Drummond's wild petunia

Acanthaceae · Texas

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Ruellia drummondiana, photograph author not stated, no rights reservedRuellia drummondiana, photograph (c) Natasha Haggard, some rights reserved (CC BY)Ruellia drummondiana, photograph (c) Chris Acree, some rights reserved (CC BY-SA)Ruellia drummondiana, photograph (c) mattmsa, some rights reserved (CC BY)Ruellia drummondiana, photograph (c) Rachel, some rights reserved (CC BY)Ruellia drummondiana, photograph (c) Rachel, some rights reserved (CC BY) 67 photographs ›
Habitat figures
Cold floor (1 night in 100)
-3.6°C
Record low -11.0 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
34°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
883mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
17–43DLI
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

Ruellia drummondiana (syn. Dipteracanthus drummondianus Nees), also known as Drummond's wild petunia, is a flowering plant endemic to central Texas in the United States. It was first collected by naturalist Thomas Drummond and first described in 1847. R. drummondiana stands up to 3' with an herbaceous dark green ridged stem and purple flowers. Unlike the majority of Ruellia in the United States, R. drummondiana produces fruit with only 2–4 seeds, as opposed to 6–20 as is common throughout the genus.

Quoted from Wikipedia, "Ruellia drummondiana", CC BY-SA 4.0.

About the genus · Ruellia

Ruellia is a genus of flowering plants commonly known as ruellias or wild petunias. They are not closely related to petunias (Petunia) although both genera belong to the same euasterid clade. The genus was named in honor of Jean Ruelle (1474–1537), herbalist and physician to Francis I of France and translator of several works of Dioscorides.

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

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (658 mm of 878 mm) takes 8 months, March to July and September to November. Mean temperature moves 19.0 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to January and March to May.

Rain

878 mm in the median year at the habitat, 658 mm of it March to July and September to November. Wettest month June at 112 mm, driest months (2 at 53 mm). Across the grid cells of the range the year's total runs 803 mm to 936 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 883 mm, is the year's rain at the top of the page; the 878 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: 17 to 43 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 17, the highest 90th-percentile month 44).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -3.6 °C, the absolute minimum -11.0 °C, 677 frost nights in 44 years, 15.4 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 40.5 °C. Monthly means: the coldest month's mean nightly low 6.0 °C in January (across the grid cells of the range 5.1 °C to 6.8 °C), the warmest month's mean daily high 34.4 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: -3.6 °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: 55 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 +8 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 Ruellia drummondiana through the yearWarmest months July and August, mean daily high 34 °C; coldest month January, mean nightly low 6.0 °C; 878 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.-20°-10°0°10°20°30°40°50°frost40.5° 99th-percentile day, NASA POWER-11.0° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125mm rainDLI 17–43RH 55–60%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 188 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 °C17 / 16–1719 / 18–1922 / 22–2326 / 26–2729 / 29–3032 / 32–3334 / 33–3534 / 33–3531 / 30–3226 / 26–2721 / 20–2217 / 16–18
Night °C6 / 5–78 / 7–811 / 10–1215 / 14–1619 / 19–2022 / 22–2324 / 23–2424 / 23–2521 / 20–2216 / 16–1711 / 11–127 / 6–8
Rain mm53 / 43–5855 / 47–6568 / 61–8164 / 55–72100 / 89–112112 / 103–12061 / 48–7953 / 47–6079 / 73–86103 / 92–11271 / 56–7759 / 44–66
DLI19 / 19–2023 / 23–2429 / 29–3035 / 35–3637 / 37–3841 / 40–4243 / 43–4441 / 40–4134 / 33–3426 / 26–2720 / 20–2117 / 17–18
RH %58 / 57–5857 / 57–5857 / 56–5857 / 56–5760 / 59–6159 / 58–6057 / 55–5855 / 54–5657 / 55–5757 / 56–5858 / 57–5858 / 57–58
How this section is made
Each figure is the median across the 188 grid cells holding the 716 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 1208:1605 (29.575, -99.725). Over 44 years there: absolute minimum -11.0 °C, 1st-percentile night -3.6 °C, 99th-percentile day 40.5 °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 188 distinct grid cells holding 716 of the 716 in-range records; extremes and elevation at the typical cell 1208:1605 (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 29.50_-100.000, lapse-corrected +8 m at 6.5 °C/km. Elevation: ETOPO 2022, 451 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.
NativeTexas · 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 marker30.248, -97.796 · in the densest population, 771 records (97% 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 793 georeferenced records inside the native range; the climate across the range on the 716 of them placed to within 10 km; the map shows only the 188 openly licensed ones, which alone would put the marker 3 km away. 1 record outside the WCVP native range not used. 77 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 793 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Ruellia drummondiana, photograph 1did not loadRuellia drummondiana, photograph 2did not loadRuellia drummondiana, photograph 3did not loadRuellia drummondiana, photograph 4did not loadRuellia drummondiana, photograph 5did not loadRuellia drummondiana, photograph 6did not load

Photographs: author not stated, no rights reserved · CC0; (c) Natasha Haggard, some rights reserved (CC BY); (c) Chris Acree, some rights reserved (CC BY-SA); (c) mattmsa, some rights reserved (CC BY); (c) Rachel, some rights reserved (CC BY) (2).

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

Tradescantia gigantea Tradescantia gigantea Giant spiderwort Photo: CC BY-SA, Turner BrockmanTinantia anomala Tinantia anomala False dayflower Photo: CC0, Karen WilsonPavonia lasiopetala Pavonia lasiopetala Texas swamp-mallow Photo: CC BY, Gary RogersZephyranthes drummondii Zephyranthes drummondii Prairie lily Photo: CC BY, NikokinCirsium texanum Cirsium texanum Texas thistle Photo: CC0, author not statedArgemone albiflora Argemone albiflora Bluestem pricklypoppy Photo: CC BY, saltyhiker

Other Ruellia 37 in the reference

Ruellia affinis Ruellia affinis Acanthaceae Photo: CC BY, B. PhalanRuellia angustiflora Ruellia angustiflora Acanthaceae Photo: CC BY, William Stephens Ruellia angustifolia Acanthaceae Ruellia blechum Ruellia blechum Browne's blechum Photo: CC BY, Guillaume Delaitre Ruellia blumei Acanthaceae Ruellia bourgaei Ruellia bourgaei Acanthaceae Photo: CC0, author not statedRuellia breedlovei Ruellia breedlovei Acanthaceae Photo: CC BY, Neptalí Ramírez MarcialRuellia brevifolia Ruellia brevifolia Tropical wild petunia Photo: CC BY, Zoe Anthony QuestedRuellia californica Ruellia californica Acanthaceae Photo: CC BY, DrepanostomaRuellia caroliniensis Ruellia caroliniensis Carolina wild petunia Photo: CC BY, portulacaRuellia chartacea Ruellia chartacea Peruvian wild petunia Photo: CC BY, Yuri SofronovRuellia ciliatiflora Ruellia ciliatiflora Hairyflower wild petunia Photo: CC BY, Reanne ("Bean") Dunn all 38 ›

Names & registers

Also known as Dipteracanthus drummondianus; Dipteracanthus lindheimerianus. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Acanthaceae
Described by
(Nees) A.Gray
Native to
Texas
Wild records
793 in range · 188 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 2026-10-22
GBIF species record gbif.species answeredasked 2026-10-22
GBIF synonyms gbif.synonyms answeredasked 2026-10-22
GBIF common names gbif.vernacular answeredasked 2026-10-22names fetched 2026-10-22
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; 153 records within 1 km of a botanic garden, herbarium or zoo left out (55 at a botanic garden or arboretum, 59 at a herbarium, 39 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-22
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-22NASA POWER (MERRA-2) daily 1981–2024, cell 29.50_-100.000, lapse-corrected +8 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-22
Wikipedia wikipedia answeredasked 2026-10-22
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 2026-10-22
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 12 datasets via GBIF.org; each carries its own licence.

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