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Wilkesia gymnoxiphium; photograph (c) Skyler K, some rights reserved (CC BY) CC BY(c) Skyler K, some rights reserved (CC BY) · observed growing wild · 2025-11-11

Wilkesia gymnoxiphium A.Gray

Iliau; Kaua'i Greensword

Asteraceae · Hawaii

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Wilkesia gymnoxiphium, photograph (c) Kevin Faccenda, some rights reserved (CC BY)Wilkesia gymnoxiphium, photograph (c) Kevin Faccenda, some rights reserved (CC BY)Wilkesia gymnoxiphium, photograph (c) Skyler K, some rights reserved (CC BY)Wilkesia gymnoxiphium, photograph (c) Skyler K, some rights reserved (CC BY)Wilkesia gymnoxiphium, photograph (c) Skyler K, some rights reserved (CC BY)Wilkesia gymnoxiphium, photograph (c) Skyler K, some rights reserved (CC BY) 51 photographs ›
Habitat figures
Coldest month, mean nightly low
17.3°C
Feb at the habitat, not a floor; extremes not used (sea cell) CHELSA
Warmest month, mean daily high
25°C
Aug and Sep at the habitat CHELSA
Rain a year (median across the range)
2,491mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
25–44DLI
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

Wilkesia gymnoxiphium (Hawaiian iliau), is a species of flowering plant in the family Asteraceae that is endemic to the island of Kauaʻi in Hawaiʻi. It is classified as endangered on the IUCN Red List. Wilkesia is one of three genera, with Argyroxiphium (silverswords and greenswords) and Dubautia (a larger group with many varied species) that are believed to be descendant from a single species related to the North American tarweed. The members of these three genera constitute what is called the silversword alliance, a group whose exceedingly close genetic heritage is not reflected in their exceptionally diverse morphologies.

Quoted from Wikipedia, "Wilkesia gymnoxiphium", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (1,858 mm of 2,468 mm) takes 8 months, October to April and August. Mean temperature moves 4.1 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: February and April to October.

Rain

2,468 mm in the median year at the habitat, 1,858 mm of it October to April and August. Wettest month December at 291 mm, driest month June at 121 mm. Across the grid cells of the range the year's total runs 1,804 mm to 2,711 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 2,491 mm, is the year's rain at the top of the page; the 2,468 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: 25 to 44 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 44).

Warmth and air
Temperature

Monthly means: the coldest month's mean nightly low 17.3 °C in February (across the grid cells of the range 15.0 °C to 19.8 °C), the warmest month's mean daily high 24.8 °C in August and September (median year across the grid cells of the range, CHELSA). Cold floor: none read. The nearest figure is 17.3 °C, the coldest month's mean nightly low, February, in the median year (CHELSA); a month's mean of its nightly lows is warmer than the nights a floor is read from. The daily extremes were read at a weather cell that is mostly sea and are not used.

Humidity

Relative humidity at the habitat: 65 to 67% 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. CHELSA monthly means, median year across the grid cells of the range. No cold floor is read without a daily extremes series; the coldest month's mean nightly low named in its sentence is not one. 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 Wilkesia gymnoxiphium through the yearWarmest months August and September, mean daily high 25 °C; coldest month February, mean nightly low 17.3 °C; 2,468 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA. Habitat months, northern hemisphere.10°15°20°25°30°°C · day and nightcold quarter0100200300400mm rainDLI 25–44RH 65–67%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 10 habitat cells, CHELSA cold quarter: the three months around the coldest month's mean nightly low DLI, mol/m²/dayRH %each on its own scale
Figures by month
JanFebMarAprMayJunJulAugSepOctNovDec
Day °C21 / 18–2320 / 18–2321 / 18–2421 / 19–2423 / 20–2524 / 21–2624 / 22–2625 / 22–2725 / 22–2724 / 22–2623 / 20–2522 / 19–24
Night °C18 / 16–2017 / 15–2018 / 15–2018 / 15–2119 / 16–2120 / 18–2221 / 18–2321 / 19–2321 / 19–2321 / 18–2320 / 17–2219 / 16–21
Rain mm245 / 198–275202 / 161–229256 / 189–275200 / 133–225167 / 119–183121 / 83–139167 / 112–200172 / 119–206155 / 110–172216 / 160–231276 / 206–308291 / 233–324
DLI26 / 22–2831 / 28–3236 / 34–3740 / 39–4142 / 42–4344 / 43–4443 / 43–4342 / 41–4239 / 37–4033 / 30–3427 / 24–2925 / 21–26
RH %66 / 62–6966 / 62–6866 / 62–6866 / 62–6865 / 62–6866 / 62–6866 / 62–6866 / 62–6865 / 62–6766 / 62–6867 / 63–6966 / 63–69

The daily extremes were read at a NASA POWER cell that is 40% land: neither it nor the next candidates whose coldest month's mean nightly low is within 2 °C of the median across cells sit in a POWER cell that is mostly land, and the rule reads a cold floor only from a cell that is mostly land, so none is read for this species. Nor is the coldest month's mean nightly low taken as one: it is a mean of a month's lows, not its coldest night. What that cell gave over 44 years: absolute minimum 14.8 °C, 1st-percentile night 16.8 °C, 99th-percentile day 25.4 °C.

How this section is made
Each figure is the median across the 10 grid cells holding the 49 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 1359:406 (22.025, -159.675). 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 10 distinct grid cells holding 49 of the 49 in-range records; extremes and elevation at the typical cell 1359:406 (its coldest month's mean nightly low nearest the median across cells, though its NASA POWER cell is only 40% land and none of the 4 next candidates within 2 °C of the median was mostly land); its position is the cell centre. Extremes: NASA POWER (MERRA-2) daily 1981–2024, cell 22.00_-159.375, lapse-corrected +408 m at 6.5 °C/km. Elevation: ETOPO 2022, 470 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.
NativeHawaii · 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 marker22.058, -159.663 · in the densest population, 122 records (99% of those in range)
Evidence usedThe map marker rests on all 123 georeferenced records inside the native range; the climate across the range on the 49 of them placed to within 10 km; the map shows only the 24 openly licensed ones, which alone would put the marker 2 km away. 74 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 123 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Wilkesia gymnoxiphium, photograph 1did not loadWilkesia gymnoxiphium, photograph 2did not loadWilkesia gymnoxiphium, photograph 3did not loadWilkesia gymnoxiphium, photograph 4did not loadWilkesia gymnoxiphium, photograph 5did not loadWilkesia gymnoxiphium, photograph 6did not load

Photographs: (c) Kevin Faccenda, some rights reserved (CC BY) (2); (c) Skyler K, some rights reserved (CC BY) (4).

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

Lipochaeta connata Nehe Cibotium menziesii Cibotium menziesii Hawaiian tree fern Photo: CC BY, Kevin FaccendaMetrosideros polymorpha Metrosideros polymorpha 'Ohi'a lehua Photo: CC0, author not stated Pipturus kauaiensis Kauai pipturus Rhus sandwicensis Rhus sandwicensis Hawaiian sumac Photo: CC BY, Sawyer BaranPipturus albidus Pipturus albidus Waimea Mamaki Photo: CC BY, Brynn Fricke

Names & registers

Also known as Argyroxiphium gymnoxiphium; Dubautia gymnoxiphium. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Asteraceae
Described by
A.Gray
Native to
Hawaii
Wild records
123 in range · 24 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; 5 records within 1 km of a botanic garden, herbarium or zoo left out (5 at a botanic garden or arboretum; 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 22.00_-159.375, lapse-corrected +408 m at 6.5 °C/km; read, and set aside: NASA POWER's cell is mostly sea (40% land), so no cold floor is shown
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 6 datasets via GBIF.org; each carries its own licence.

Cultifolio

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