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An example collection, so you can see what this page does. Nothing added here is kept: leaving deletes it.
Psilotum × complanatum; photograph (c) Richard Littauer, some rights reserved (CC BY) CC BY(c) Richard Littauer, some rights reserved (CC BY) · observed growing wild · 2026-08-23

Psilotum × complanatum Sw.

Flatfork fern

Psilotaceae · Hawaii, Mexico Central +13

A hybrid: P. flaccidum × P. nudum, the parents Kew's World Checklist states for it (WCVP, RBG Kew).

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Psilotum × complanatum, photograph (c) Neal Kelso, some rights reserved (CC BY)Psilotum × complanatum, photograph (c) Neal Kelso, some rights reserved (CC BY)Psilotum × complanatum, photograph (c) nmoorhatch, some rights reserved (CC BY)Psilotum × complanatum, photograph (c) nmoorhatch, some rights reserved (CC BY)Psilotum × complanatum, photograph (c) David Anderson, some rights reserved (CC BY)Psilotum × complanatum, photograph (c) David Anderson, some rights reserved (CC BY) 58 photographs ›
Habitat figures
Cold floor (1 night in 100)
12.2°C
Record low 9.8 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
24°C
May, Jun, Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,833mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
26–41DLI
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 summers: the rain comes June to November, read as a summer growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

Summary

Psilotum complanatum, the flatfork fern, is a rare herbaceous epiphytic fern ally in the genus Psilotum. There is some evidence that it might be a true fern that has lost some typically fern-like characteristics.

Quoted from Wikipedia, "Psilotum complanatum", CC BY-SA 4.0.

About the genus · Psilotum

Psilotum is a genus of fern-like vascular plants. It is one of two genera in the family Psilotaceae commonly known as whisk ferns, the other being Tmesipteris. Plants in these two genera were once thought to be descended from the earliest surviving vascular plants, but more recent phylogenies place them as basal ferns, as a sister group to Ophioglossales. More on Wikipedia ›

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

Cultivation

Seasons

The rain rule reads a summer growing season: 70% of the median year's rain (1,215 mm of 1,689 mm) falls in June to November, warmer than the year (wet-season mean 20.3 °C against a yearly mean of 19.3 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: December to May.

Rain

1,689 mm in the median year at the habitat, 1,215 mm of it June to November. Wettest month July at 250 mm, driest month March at 63 mm. Across the grid cells of the range the year's total runs 1,028 mm to 3,469 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,833 mm, is the year's rain at the top of the page; the 1,689 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: 26 to 41 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 47).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is 12.2 °C, the absolute minimum 9.8 °C, no frost in 44 years (NASA POWER daily minima). Warmest: the 99th-percentile day is 22.6 °C. Monthly means: the coldest month's mean nightly low 12.9 °C in January (across the grid cells of the range 7.6 °C to 19.4 °C), the warmest month's mean daily high 24.1 °C in June (median year across the grid cells of the range, CHELSA). Cold floor: 12.2 °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: 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 +680 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 Psilotum × complanatum through the yearWarmest months May, June, July and August, mean daily high 24 °C; coldest month January, mean nightly low 12.9 °C; 1,689 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.5°10°15°20°25°30°35°22.6° 99th-percentile day, NASA POWER9.8° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400500mm rainDLI 26–41RH 64–68%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 123 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 °C21 / 18–2421 / 18–2522 / 18–2723 / 19–2924 / 20–2924 / 20–2924 / 21–2724 / 21–2823 / 21–2723 / 20–2722 / 19–2521 / 18–24
Night °C13 / 8–1913 / 8–1914 / 10–1915 / 12–2017 / 13–2117 / 14–2217 / 14–2218 / 14–2318 / 14–2317 / 12–2215 / 10–2114 / 8–20
Rain mm73 / 17–31065 / 12–28763 / 9–39783 / 18–310107 / 47–242189 / 42–318250 / 53–349234 / 52–328242 / 53–368183 / 78–322117 / 18–40883 / 10–374
DLI27 / 22–3332 / 26–3836 / 32–4440 / 36–4741 / 38–4640 / 35–4640 / 34–4639 / 34–4436 / 30–4133 / 27–3628 / 24–3326 / 21–31
RH %66 / 51–6965 / 49–6864 / 46–6964 / 47–7066 / 53–6967 / 61–7067 / 62–7167 / 63–7168 / 63–7168 / 60–7067 / 56–7066 / 53–69
How this section is made
Each figure is the median across the 123 grid cells holding the 253 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 1411:494 (19.425, -155.275). Over 44 years there: absolute minimum 9.8 °C, 1st-percentile night 12.2 °C, 99th-percentile day 22.6 °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 123 distinct grid cells holding 253 of the 253 in-range records; extremes and elevation at the typical cell 1411:494 (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 19.50_-155.000, lapse-corrected +680 m at 6.5 °C/km. Elevation: ETOPO 2022, 1162 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, Mexico Central, Mexico Northeast, Mexico Gulf, Mexico Northwest, Mexico Southwest, El Salvador, Guatemala, Honduras, Haiti, Jamaica, Leeward Is. AB Ant, Puerto Rico, Venezuela, Ecuador · 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 marker21.33, -157.785 · in the densest population, 221 records (58% of those in range)
Kew's description“epiphyte or lithophyte” · “wet tropical” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 381 georeferenced records inside the native range; the climate across the range on the 253 of them placed to within 10 km; the map shows only the 212 openly licensed ones, which alone would put the marker 6265 km away. 446 records outside the WCVP native range not used. 128 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 inside the densest 2° block of the 381 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Psilotum × complanatum, photograph 1did not loadPsilotum × complanatum, photograph 2did not loadPsilotum × complanatum, photograph 3did not loadPsilotum × complanatum, photograph 4did not loadPsilotum × complanatum, photograph 5did not loadPsilotum × complanatum, photograph 6did not load

Photographs: (c) Neal Kelso, some rights reserved (CC BY) (2); (c) nmoorhatch, some rights reserved (CC BY) (2); (c) David Anderson, 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.

Jacquiniella teretifolia Jacquiniella teretifolia Moss tufted orchid Photo: CC BY, fmunozOreopanax capitatus Oreopanax capitatus Broad-leaved balsam Photo: CC BY, Guillaume DelaitreCyclopogon elatus Cyclopogon elatus Tall ladies'-tresses Photo: CC0, author not stated Begonia ludicra Begoniaceae Disocactus macranthus Disocactus macranthus Cactaceae Photo: Public domain, DaderotPhoradendron nervosum Phoradendron nervosum Viscaceae Photo: CC BY, Nicolás Baresch Uribe

Other Psilotum 1 in the reference

Psilotum nudum Psilotum nudum Whisk fern Photo: CC BY-SA, Douglas Goldman

Names & registers

Also known as Bernhardia complanata; Bernhardia schiedeana; Psilotum complanatum var. flaccidum; Psilotum complanatum var. latissimum; Psilotum complanatum var. mexicanum and 1 more. (GBIF Backbone)

Kew accepts as species of their own Psilotum flaccidum: older names in GBIF's record of this species that Kew's World Checklist accepts as other species. (WCVP, RBG Kew, file of 2026-06-04)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Psilotaceae
Described by
Sw.
Native to
Hawaii, Mexico Central, Mexico Northeast +12
Wild records
381 in range · 212 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; 9 records within 1 km of a botanic garden, herbarium or zoo left out (4 at a botanic garden or arboretum, 5 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 19.50_-155.000, lapse-corrected +680 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 96 datasets via GBIF.org; each carries its own licence.

Cultifolio

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