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Clematis japonica; photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY) CC BY(c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY) · observed growing wild · 2026-04-26

Clematis japonica Thunb.

Ranunculaceae · Japan · listed by its genus as a temperate garden plant

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Clematis japonica, photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY)Clematis japonica, photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY)Clematis japonica, photograph (c) Hector Montero, some rights reserved (CC BY)Clematis japonica, photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY)Clematis japonica, photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY)Clematis japonica, photograph (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY) 47 photographs ›
Habitat figures
Cold floor (1 night in 100)
-11.5°C
Record low -16.9 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
26°C
Aug at the habitat CHELSA
Rain a year (median across the range)
1,784mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
16–34DLI
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 March and May to October, read as a summer growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

About the genus · Clematis

Clematis is a genus of about 380 species within the buttercup family, Ranunculaceae. Their garden hybrids and cultivars have been popular among gardeners, beginning with Clematis 'Jackmanii', a garden staple since 1862. More cultivars are being produced constantly, mainly of Chinese and Japanese origin.

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

Cultivation

Grouped as a temperate garden plant, listed under the genus Clematis in the archetype table, and Kew describes it as “climbing subshrub”, “temperate”.

Seasons

The rain rule reads a summer growing season: 70% of the median year's rain (1,366 mm of 1,796 mm) falls in March and May to October, warmer than the year (wet-season mean 16.2 °C against a yearly mean of 10.8 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: November to April and September.

Rain

1,796 mm in the median year at the habitat, 1,366 mm of it March and May to October. Wettest month September at 254 mm, driest month December at 56 mm. Across the grid cells of the range the year's total runs 1,355 mm to 2,744 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,784 mm, is the year's rain at the top of the page; the 1,796 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: 16 to 34 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 14, the highest 90th-percentile month 37).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -11.5 °C, the absolute minimum -16.9 °C, 4,522 frost nights in 44 years, 102.8 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 30.5 °C. Monthly means: the coldest month's mean nightly low -8.1 °C in January (across the grid cells of the range -14.4 °C to -0.2 °C), the warmest month's mean daily high 25.9 °C in August (median year across the grid cells of the range, CHELSA). Cold floor: -11.5 °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: 58 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 -581 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.

Group. Listed under the genus Clematis in the archetype table, and Kew describes it as “climbing subshrub”, “temperate”. A group is taken only where Kew's description of the species agrees with the table's listing. The table gives no figure and no prose; the cold floor is the habitat's alone.

Climate across the habitat

Habitat months, northern hemisphere

Habitat climate of Clematis japonica through the yearWarmest month August, mean daily high 26 °C; coldest month January, mean nightly low -8.1 °C; 1,796 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°frost30.5° 99th-percentile day, NASA POWER-16.9° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0100200300400mm rainDLI 16–34RH 58–68%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 134 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 °C2 / -4–83 / -3–87 / 1–1113 / 7–1718 / 13–2121 / 17–2425 / 20–2726 / 21–2922 / 18–2517 / 12–2011 / 5–156 / -1–10
Night °C-8 / -14–0-7 / -13–0-2 / -8–34 / -2–99 / 3–1414 / 8–1818 / 13–2119 / 13–2315 / 10–209 / 3–142 / -4–8-4 / -10–3
Rain mm65 / 44–11378 / 48–125136 / 81–220132 / 92–219158 / 119–254207 / 157–332228 / 163–356203 / 132–286254 / 191–354180 / 124–25199 / 69–15456 / 38–94
DLI18 / 16–2123 / 21–2628 / 25–3133 / 31–3634 / 32–3730 / 28–3430 / 28–3332 / 29–3325 / 23–2621 / 19–2317 / 16–1916 / 14–18
RH %58 / 55–6458 / 55–6258 / 56–6158 / 56–6161 / 58–6465 / 61–6968 / 64–7066 / 63–7066 / 63–6962 / 60–6560 / 58–6358 / 55–62
How this section is made
Each figure is the median across the 134 grid cells holding the 170 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 1093:6358 (35.325, 137.925). Over 44 years there: absolute minimum -16.9 °C, 1st-percentile night -11.5 °C, 99th-percentile day 30.5 °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 134 distinct grid cells holding 170 of the 170 in-range records; extremes and elevation at the typical cell 1093:6358 (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 35.50_138.125, lapse-corrected -581 m at 6.5 °C/km. Elevation: ETOPO 2022, 788 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.
NativeJapan · 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 marker35.59, 139.08 · in the densest population, 691 records (72% of those in range)
Kew's description“climbing subshrub” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 964 georeferenced records inside the native range; the climate across the range on the 170 of them placed to within 10 km; the map shows only the 889 openly licensed ones, which alone would put the marker in the same place. 794 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 964 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Clematis japonica, photograph 1did not loadClematis japonica, photograph 2did not loadClematis japonica, photograph 3did not loadClematis japonica, photograph 4did not loadClematis japonica, photograph 5did not loadClematis japonica, photograph 6did not load

Photographs: (c) WATANABE Hitoshi 渡辺仁, some rights reserved (CC BY) (5); (c) Hector Montero, some rights reserved (CC BY).

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

Fagus japonica Fagus japonica Japanese Blue Beech Photo: CC BY, りなべるEuptelea polyandra Euptelea polyandra Japanese Euptelea Photo: CC BY, W RaoAcer carpinifolium Acer carpinifolium Hornbeam maple Photo: CC0, author not statedHakonechloa macra Hakonechloa macra Hakone grass Photo: CC BY-SA, User:SB_JohnnyBuckleya lanceolata Buckleya lanceolata Thesiaceae Photo: CC BY-SA, Qwert1234Aster microcephalus Aster microcephalus Asteraceae Photo: CC BY, Kai Löhr

Other Clematis 112 in the reference

Clematis addisonii Clematis addisonii Addison Brown's clematis Photo: CC0, author not statedClematis aethusifolia Clematis aethusifolia Parsley-leaf clematis Photo: CC BY, zhangshenClematis afoliata Clematis afoliata Rush-stem clematis Photo: CC BY, Rock McLaren Clematis akebioides Ranunculaceae Clematis akoensis Clematis akoensis Ranunculaceae Photo: CC0, 葉子Clematis albicoma Clematis albicoma White-haired leather-flower Photo: CC BY, Alaina KrakowiakClematis alpina Clematis alpina Alpine Clematis Photo: CC0, author not statedClematis apiifolia Clematis apiifolia Three-leaf clematis Photo: CC BY, Timur KalininskyClematis aristata Clematis aristata Goat's-beard Photo: CC BY, Ian RainbowClematis armandii Clematis armandii Evergreen Clematis Photo: CC0, author not stated Clematis aureolata Ranunculaceae Clematis brachiata Clematis brachiata Traveler's-joy Photo: CC0, author not stated all 113 ›

Names & registers

Also known as Atragene japonica; Atragene polypetala; Clematis japonica f. cremea; Clematis japonica f. villosula; Clematis japonica var. cremea and 5 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataiNaturalist

The record

Family
Ranunculaceae
Described by
Thunb.
Native to
Japan
Wild records
964 in range · 889 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 2026-10-21
GBIF species record gbif.species answeredasked 2026-10-21
GBIF synonyms gbif.synonyms answeredasked 2026-10-21
GBIF common names gbif.vernacular answeredasked 2026-10-21names fetched 2026-10-21
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; 24 records within 1 km of a botanic garden, herbarium or zoo left out (11 at a botanic garden or arboretum, 13 at a zoo; Wikidata's list)
Habitat climate climate answeredasked 2026-10-21
Daily extremes (NASA POWER) climate.extremes answeredasked 2026-10-21NASA POWER (MERRA-2) daily 1981–2024, cell 35.50_138.125, lapse-corrected -581 m at 6.5 °C/km
Wikidata wikidata answeredasked 2026-10-21IPNI and POWO linked by Kew's number for Clematis japonica Thunb. (the item's: IPNI 927388-1, POWO 709806-1)
Wikipedia wikipedia nothing to reportasked 2026-10-21
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 2026-10-21
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 42 datasets via GBIF.org; each carries its own licence.

Cultifolio

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