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Persicaria microcephala; photograph author not stated, no rights reserved CC0author not stated, no rights reserved · observed growing wild · 2023-11-11

Persicaria microcephala (D.Don) H.Gross

Polygonaceae · China South-Central, China North-Central +8

Cited as Kew's World Checklist cites it, Persicaria microcephala (D.Don) H.Gross: GBIF's backbone key for this page carries the name with another author, (Wall. ex D.Don) Sasaki.

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Persicaria microcephala, photograph (c) Brian Magurn, some rights reserved (CC BY)Persicaria microcephala, photograph author not stated, no rights reservedPersicaria microcephala, photograph author not stated, no rights reservedPersicaria microcephala, photograph (c) Sagnik Dutta Roy, some rights reserved (CC BY)Persicaria microcephala, photograph (c) Sagnik Dutta Roy, some rights reserved (CC BY)Persicaria microcephala, photograph (c) Sagnik Dutta Roy, some rights reserved (CC BY) 29 photographs ›
Habitat figuresfrom few records
Coldest month, mean nightly low
5.9°C
Jan at the habitat, not a floor; extremes not used (the weather cell's ground is too far off) CHELSA
Warmest month, mean daily high
26°C
Jun at the habitat CHELSA
Rain a year (median across the range)
3,043mm
10 months of 25 mm or more in the median year CHELSA
Open-sky light
23–42DLI
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 September, read as a summer growing season. rain rule, CHELSA
Northern hemisphere unless you set your site. The chart is in the habitat's months.

From few records: 4 records in 4 grid cells. The records.

Summary

Persicaria microcephala (syn. Polygonum microcephalum), the small-headed knotweed, is a species of flowering plant in the family Polygonaceae. It is native to the Himalayas, and central and southern China, and it has been introduced to Great Britain. Its cultivar 'Red Dragon' has gained the Royal Horticultural Society's Award of Garden Merit.

Quoted from Wikipedia, "Persicaria microcephala", CC BY-SA 4.0.

Cultivation

Seasons

The rain rule reads a summer growing season: 70% of the median year's rain (2,402 mm of 2,965 mm) falls in June to September, warmer than the year (wet-season mean 23.4 °C against a yearly mean of 18.6 °C). Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: December to March.

Rain

2,965 mm in the median year at the habitat, 2,402 mm of it June to September. Wettest month July at 797 mm, driest month December at 17 mm. Across the grid cells of the range the year's total runs 1,793 mm to 3,171 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 3,043 mm, is the year's rain at the top of the page; the 2,965 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: 23 to 42 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 16, the highest 90th-percentile month 45).

Warmth and air
Temperature

Monthly means: the coldest month's mean nightly low 5.9 °C in January (across the grid cells of the range -0.6 °C to 10.5 °C), the warmest month's mean daily high 25.6 °C in June (median year across the grid cells of the range, CHELSA). Cold floor: none read. The nearest figure is 5.9 °C, the coldest month's mean nightly low, January, 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 whose ground is too far above or below the typical spot to correct for, and are not used.

Humidity

Relative humidity at the habitat: 55 to 73% 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

From few records: this habitat climate is read from 4 records in 4 grid cells; a page says so under 12 records or 5 cells, and shows the figures as read.

Habitat months, northern hemisphere

Habitat climate of Persicaria microcephala through the yearWarmest month June, mean daily high 26 °C; coldest month January, mean nightly low 5.9 °C; 2,965 mm of rain in the median year (the twelve monthly medians added). Medians across the range, from CHELSA. Habitat months, northern hemisphere.-10°0°10°20°30°40°frost°C · day and nightcold quarter02004006008001000mm rainDLI 23–42RH 55–73%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 4 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 °C16 / 12–2217 / 12–2521 / 16–3024 / 19–3425 / 21–3626 / 23–3325 / 22–2825 / 22–2725 / 21–2823 / 19–2820 / 16–2617 / 13–23
Night °C6 / -1–117 / 0–129 / 3–1612 / 6–2116 / 11–2519 / 15–2521 / 17–2320 / 17–2219 / 14–2214 / 9–1811 / 5–148 / 2–11
Rain mm28 / 26–3336 / 24–4166 / 30–7197 / 32–125207 / 63–239468 / 231–547797 / 497–844688 / 461–758449 / 301–47294 / 50–11018 / 14–2917 / 14–19
DLI25 / 17–2930 / 22–3537 / 30–4142 / 36–4540 / 35–4432 / 29–3523 / 22–2423 / 22–2527 / 23–2930 / 24–3326 / 20–3024 / 16–28
RH %55 / 52–6055 / 49–6055 / 45–5755 / 41–5861 / 45–6468 / 57–6973 / 68–7472 / 70–7369 / 65–7061 / 54–6358 / 51–6056 / 52–59

The daily extremes were not used: the correction for elevation, -1788 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's. So no cold floor is read for this species, and the coldest month's mean nightly low is not taken as one. What that cell gave, so corrected, over 44 years: absolute minimum -6.1 °C, 1st-percentile night 3.3 °C.

How this section is made
Each figure is the median across the 4 grid cells holding the 4 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 1234:5278 (28.275, 83.925). 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 4 distinct grid cells holding 4 of the 4 in-range records; extremes and elevation at the typical cell 1234:5278 (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 28.50_83.750, lapse-corrected -1788 m at 6.5 °C/km. Elevation: ETOPO 2022, 1254 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.
NativeChina South-Central, China North-Central, China Southeast, Tibet, Assam, Bangladesh, East Himalaya, India, Nepal, West Himalaya · introduced: Great Britain · 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 marker29.49, 103.39 · in the densest population, 49 records (43% of those in range)
Kew's description“perennial” · “temperate” · quoted from WCVP, RBG Kew (CC BY 4.0); not derived here
Evidence usedThe map marker rests on all 113 georeferenced records inside the native range; the climate across the range on the 4 of them placed to within 10 km; the map shows only the 78 openly licensed ones, which alone would put the marker 1228 km away. 55 records outside the WCVP native range not used. Under a dozen records behind the climate. 109 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 4° block of the 113 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Persicaria microcephala, photograph 1did not loadPersicaria microcephala, photograph 2did not loadPersicaria microcephala, photograph 3did not loadPersicaria microcephala, photograph 4did not loadPersicaria microcephala, photograph 5did not loadPersicaria microcephala, photograph 6did not load

Photographs: (c) Brian Magurn, some rights reserved (CC BY); author not stated, no rights reserved · CC0 (2); (c) Sagnik Dutta Roy, some rights reserved (CC BY) (3).

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

Bulbophyllum careyanum Bulbophyllum careyanum Orchidaceae Photo: CC0, Daderot Stranvaesia nussia Rosaceae Vanda alpina Vanda alpina Orchidaceae Photo: CC BY-SA, OrchiBegonia hatacoa Begonia hatacoa Begoniaceae Photo: CC BY, KarishmaPaphiopedilum venustum Paphiopedilum venustum Laddy's Slipper Orchid Photo: CC BY-SA, Dalton Holland BaptistaDendrobium jenkinsii Dendrobium jenkinsii Orchidaceae Photo: CC BY, Steven Whitebread

Other Persicaria 42 in the reference

Persicaria acuminata Persicaria acuminata Tapertip Smartweed Photo: CC BY, Seba FernándezPersicaria amphibia Persicaria amphibia Amphibious bistort Photo: CC BY, Sandy WolkenbergPersicaria arifolia Persicaria arifolia Halberd-leaved tearthumb Photo: CC BY-SA, V. Ross JohnsonPersicaria attenuata Persicaria attenuata Watersmart Weed Photo: CC0, author not statedPersicaria barbata Persicaria barbata Bearded knotweed Photo: CC BY, chiuluanPersicaria biconvexa Persicaria biconvexa Polygonaceae Photo: CC0, 葉子Persicaria bicornis Persicaria bicornis Pink smartweed Photo: CC0, author not statedPersicaria capitata Persicaria capitata Pinkhead smartweed Photo: CC0, author not statedPersicaria chinensis Persicaria chinensis Chinese knotweed Photo: CC BY, Ben CostamagnaPersicaria decipiens Persicaria decipiens Slender knotweed Photo: CC BY, Duarte FradePersicaria dichotoma Persicaria dichotoma Polygonaceae Photo: CC BY, 如此甚好Persicaria extremiorientalis Persicaria extremiorientalis Far-Eastern smartweed Photo: CC BY, Heather Mazzaccaro all 43 ›

Names & registers

Also known as Ampelygonum microcephalum; Persicaria microcephala var. microcephala; Polygonum ciliatum; Polygonum microcephalum; Polygonum microcephalum var. microcephalum and 1 more. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Polygonaceae
Described by
(D.Don) H.Gross
Native to
China South-Central, China North-Central, China Southeast +7
Wild records
113 in range · 78 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 2026-10-22GBIF's key 7291432 is Persicaria microcephala (Wall. ex D.Don) Sasaki; the page links Kew's Persicaria microcephala (D.Don) H.Gross, and the name is cited as Kew cites it
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; 24 records within 1 km of a botanic garden, herbarium or zoo left out (20 at a botanic garden or arboretum, 2 at a herbarium, 2 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 28.50_83.750, lapse-corrected -1788 m at 6.5 °C/km; read, and set aside: the correction for elevation, -1788 m, is beyond the 1,000 m either way that a lapse rate is applied over, so the weather cell's ground is other terrain than the typical spot's, 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 29 datasets via GBIF.org; each carries its own licence.

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