76 photographs › At a glance
- Jan
- Feb
- Mar
- Apr, shaded
- May, shaded
- Jun, shaded
- Jul, shaded
- Aug, shaded
- Sep, shaded
- Oct, shaded
- Nov
- Dec
Summary
Strobilanthes cusia, also known as Assam indigo or Chinese rain bell, is a perennial flowering plant of the family Acanthaceae. Native to South Asia, China, and Indochina, it was historically cultivated on a large scale in India and China as a source of indigo dye, which is also known as Assam indigo. In addition to being used for dye, it is also used in the traditional Chinese herbal medicine "Qingdai". Other names for this dicot include Pink strobilanthes and Strobilanthes flaccidifolius, where flaccidifolius is Latin for "drooping leaves".
Quoted from Wikipedia, "Strobilanthes cusia", CC BY-SA 4.0.
About the genus · Strobilanthes
Strobilanthes is a genus of about 350 species of flowering plants in the family Acanthaceae, mostly native to tropical Asia and Madagascar, but with a few species extending north into temperate regions of Asia. Many species are cultivated for their two-lipped, hooded flowers in shades of blue, pink, white and purple. Most are frost-tender and require protection in frost-prone areas. More on Wikipedia ›
Quoted from Wikipedia, "Strobilanthes", CC BY-SA 4.0.
Cultivation
Seasons
The rain rule reads a summer growing season: 70% of the median year's rain (2,495 mm of 3,314 mm) falls in April to October, warmer than the year (wet-season mean 24.7 °C against a yearly mean of 21.4 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: October to April.
Rain
3,314 mm in the median year at the habitat, 2,495 mm of it April to October. Wettest month September at 503 mm, driest month January at 114 mm. Across the grid cells of the range the year's total runs 2,327 mm to 4,538 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 3,605 mm, is the year's rain at the top of the page; the 3,314 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: 15 to 37 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 13, the highest 90th-percentile month 38).
Warmth and air
Coldest: the 1st-percentile night over 44 years at a typical spot in the range is 9.8 °C, the absolute minimum 3.5 °C, no frost in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 36.1 °C. Monthly means: the coldest month's mean nightly low 11.6 °C in January (across the grid cells of the range 8.2 °C to 13.6 °C), the warmest month's mean daily high 28.8 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: 9.8 °C, which is the 1st-percentile night over 44 years at a typical spot in the range (NASA POWER).
Relative humidity at the habitat: 64 to 68% 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 -497 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
Mean daily high from 17 °C in Jan to 29 °C in Jul; mean nightly low from 12 °C in Jan and Feb to 24 °C in Jul and Aug. The cold quarter, Dec to Feb, is the three months around the coldest month's mean nightly low, centred on the 2 months in a row that tie for it. 3,314 mm of rain in the median year (the twelve monthly medians added), the wettest month Sep. The bands show the 10th to 90th percentile across 126 habitat cells. Over 44 years at a typical spot in the range (NASA POWER) the absolute minimum was 3.5 °C and the 99th-percentile day 36.1 °C; neither is dated to a month. Beneath: daily light integral and relative humidity through the year, each on its own scale.
Figures by month
| Figure | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Day °C | 17 / 14–19 | 18 / 15–20 | 20 / 18–22 | 23 / 21–25 | 26 / 24–27 | 27 / 25–29 | 29 / 27–30 | 28 / 26–30 | 27 / 25–28 | 25 / 22–26 | 22 / 19–23 | 18 / 16–20 |
| Night °C | 12 / 8–14 | 12 / 10–14 | 14 / 12–16 | 18 / 15–20 | 21 / 18–23 | 23 / 20–25 | 24 / 20–26 | 24 / 20–26 | 22 / 19–24 | 20 / 17–22 | 17 / 13–19 | 13 / 10–15 |
| Rain mm | 114 / 26–275 | 184 / 57–340 | 192 / 80–273 | 216 / 159–254 | 329 / 278–424 | 412 / 328–598 | 338 / 231–670 | 386 / 300–702 | 503 / 287–639 | 311 / 68–590 | 201 / 39–478 | 128 / 28–313 |
| DLI | 16 / 13–24 | 18 / 15–26 | 24 / 21–31 | 29 / 26–34 | 31 / 29–33 | 32 / 30–34 | 37 / 33–38 | 34 / 30–35 | 29 / 28–31 | 23 / 21–30 | 18 / 16–25 | 15 / 13–23 |
| RH % | 65 / 62–72 | 67 / 63–72 | 67 / 64–72 | 67 / 64–72 | 67 / 64–71 | 68 / 64–72 | 67 / 64–71 | 68 / 65–72 | 68 / 65–72 | 67 / 62–72 | 66 / 61–72 | 64 / 59–70 |
How this section is made
Natural habitat
How this section is made
Photographs
Photographs: (c) 如此甚好, some rights reserved (CC BY); (c) 胡正恆(Jackson Hu), some rights reserved (CC BY) (2); (c) Yinling Chen, some rights reserved (CC BY); (c) 呂一起(Lyu yi-chi), some rights reserved (CC BY) (2).
Related
Similar habitat climate The 6 nearest by mean daily high, mean nightly low and rain, month by month. How.
Daphniphyllum pentandrum Daphniphyllaceae Photo: CC BY, Kiwi Shen
Lysimachia decurrens Primulaceae Photo: CC BY, Cheng-Te Hsu
Wendlandia formosana Rubiaceae Photo: CC BY, Yu-Huang Wang Dennstaedtia hookeriana Dennstaedtiaceae 
Pericampylus glaucus Native Grapes Photo: CC BY-SA, 許文俊Other Strobilanthes 32 in the reference
Strobilanthes alternata Red ivy Photo: CC BY, kumarkv
Strobilanthes anisophylla Goldfussia Photo: CC BY, Todd Huang
Strobilanthes atropurpurea Acanthaceae Photo: CC BY, Ramnarayan K
Strobilanthes attenuata Acanthaceae Photo: CC BY-SA, Dinesh Valke
Strobilanthes auriculata Acanthaceae Photo: CC BY, Ricci Masero
Strobilanthes callosa Acanthaceae Photo: CC BY-SA, Dinesh Valke
Strobilanthes crispa Acanthaceae Photo: CC BY, Franz Anthony
Strobilanthes cystolithigera Acanthaceae Photo: CC BY-SA, Krzysztof Ziarnek, Kenraiz Strobilanthes dimorphotricha Acanthaceae 
Strobilanthes flexicaulis Acanthaceae Photo: CC0, author not stated
Strobilanthes formosana Acanthaceae Photo: CC BY, 如此甚好 Strobilanthes glaucescens Acanthaceae all 33 ›Names & registers
Also known as Baphicacanthus cusia; Dipteracanthus calycinus; Goldfussia cusia; Ruellia cusia; Ruellia indigofera and 7 more. (GBIF Backbone)
The record
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 answeredasked 2026-10-22gbif.synonyms answeredasked 2026-10-22gbif.vernacular answeredasked 2026-10-22names fetched 2026-10-22wcvp.distribution answeredas of 2026-06-04gbif.occurrences answeredas of 2026-10-21GBIF occurrence download https://doi.org/10.15468/dl.hbdw64, of 2026-10-21; 21 records within 1 km of a botanic garden, herbarium or zoo left out (19 at a botanic garden or arboretum, 2 at a zoo; Wikidata's list)climate answeredasked 2026-10-22climate.extremes answeredasked 2026-10-22NASA POWER (MERRA-2) daily 1981–2024, cell 23.50_120.625, lapse-corrected -497 m at 6.5 °C/kmwikidata answeredasked 2026-10-22found by its label; its IPNI identifier 55627-1 is Kew's for Strobilanthes cusia (Nees) Kuntzewikipedia answeredasked 2026-10-22inat.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 2026-10-22inat.photos.cultivated not askedgbif.media answeredasked 2026-10-22openalex not askednot yet asked for this reference; a later fill takes the papers from OpenAlex's snapshotEvery 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 38 datasets via GBIF.org; each carries its own licence.