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Helianthus decapetalus; photograph (c) Tom Scavo, some rights reserved (CC BY) CC BY(c) Tom Scavo, some rights reserved (CC BY) · observed growing wild · 2026-09-07

Helianthus decapetalus L.

Thinleaf sunflower; Thin-leaved sunflower; Ten-petals sunflower; Ten-rayed sunflower

Asteraceae · New Brunswick, Ontario +32

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Helianthus decapetalus, photograph author not stated, no rights reservedHelianthus decapetalus, photograph author not stated, no rights reservedHelianthus decapetalus, photograph author not stated, no rights reservedHelianthus decapetalus, photograph (c) Tom Scavo, some rights reserved (CC BY)Helianthus decapetalus, photograph (c) Tom Scavo, some rights reserved (CC BY)Helianthus decapetalus, photograph (c) Tom Scavo, some rights reserved (CC BY) 124 photographs ›
Habitat figures
Cold floor (1 night in 100)
-13.8°C
Record low -22.8 °C in 44 years, at a typical spot in the range NASA POWER
Warmest month, mean daily high
27°C
Jul and Aug at the habitat CHELSA
Rain a year (median across the range)
1,184mm
12 months of 25 mm or more in the median year CHELSA
Open-sky light
11–39DLI
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

Helianthus decapetalus, known by the common names thinleaf sunflower, thin-leaved sunflower, and woodland sunflower, is a perennial forb in the family Asteraceae. It is native to the Eastern and Central United States and Canada, from New Brunswick west to Iowa, Wisconsin, and Ontario, south as far as Georgia and Louisiana. It produces yellow composite flowers in late summer or early fall.

Quoted from Wikipedia, "Helianthus decapetalus", CC BY-SA 4.0.

About the genus · Helianthus

Helianthus is a genus comprising around 50 species of annual and perennial flowering plants in the daisy family Asteraceae commonly known as sunflowers. The species of Helianthus are native to North America. The best-known species is the common sunflower. More on Wikipedia ›

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

Cultivation

Seasons

The rain rule reads no short rainy season: 70% of the median year's rain (831 mm of 1,175 mm) takes 8 months, March to October. Mean temperature moves 24.8 °C between the warmest and coldest month. Months are the habitat's, northern hemisphere; shifted six months for a southern-hemisphere collection: September to April.

Rain

1,175 mm in the median year at the habitat, 831 mm of it March to October. Wettest month July at 116 mm, driest month February at 75 mm. Across the grid cells of the range the year's total runs 969 mm to 1,386 mm, the 10th to 90th percentile of each cell's own year. The median of the cells' own yearly totals, 1,184 mm, is the year's rain at the top of the page; the 1,175 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: 11 to 39 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 9, the highest 90th-percentile month 41).

Warmth and air
Temperature

Coldest: the 1st-percentile night over 44 years at a typical spot in the range is -13.8 °C, the absolute minimum -22.8 °C, 4,924 frost nights in 44 years, 111.9 a year (NASA POWER daily minima). Warmest: the 99th-percentile day is 30.5 °C. Monthly means: the coldest month's mean nightly low -6.2 °C in January (across the grid cells of the range -11.9 °C to -2.4 °C), the warmest month's mean daily high 27.4 °C in July (median year across the grid cells of the range, CHELSA). Cold floor: -13.8 °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: 56 to 60% 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 -63 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 Helianthus decapetalus through the yearWarmest months July and August, mean daily high 27 °C; coldest month January, mean nightly low -6.2 °C; 1,175 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.-30°-20°-10°0°10°20°30°40°frost30.5° 99th-percentile day, NASA POWER-22.8° lowest night in 44 years, NASA POWER°C · day and nightcold quarter0255075100125150mm rainDLI 11–39RH 56–60%JanFebMarAprMayJunJulAugSepOctNovDec
day night rain medians and 10th–90th percentile across 917 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 / -3–64 / -1–89 / 5–1315 / 12–1920 / 18–2325 / 23–2827 / 25–3027 / 24–2923 / 20–2516 / 13–1910 / 7–134 / 0–8
Night °C-6 / -12–-2-5 / -10–-1-1 / -5–35 / 2–810 / 8–1315 / 13–1818 / 16–2117 / 15–2014 / 11–178 / 5–102 / 0–5-3 / -8–0
Rain mm82 / 57–10275 / 53–10294 / 65–11999 / 82–120108 / 92–131112 / 97–134116 / 99–137105 / 87–122102 / 86–12395 / 71–12294 / 77–11793 / 66–115
DLI13 / 11–1619 / 17–2026 / 25–2732 / 31–3437 / 35–3839 / 38–4138 / 37–4034 / 33–3527 / 25–2920 / 18–2313 / 11–1711 / 9–14
RH %59 / 57–6357 / 56–6156 / 55–5856 / 55–5758 / 56–5959 / 57–6159 / 58–6260 / 58–6260 / 58–6259 / 57–6159 / 57–6159 / 57–63
How this section is made
Each figure is the median across the 917 grid cells holding the 1098 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 936:2015 (43.175, -79.225). Over 44 years there: absolute minimum -22.8 °C, 1st-percentile night -13.8 °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 917 distinct grid cells holding 1098 of the 1098 in-range records; extremes and elevation at the typical cell 936:2015 (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 43.00_-79.375, lapse-corrected -63 m at 6.5 °C/km. Elevation: ETOPO 2022, 100 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.
NativeNew Brunswick, Ontario, Québec, Illinois, Iowa, Missouri, Oklahoma, Wisconsin, Connecticut, Indiana, Maine, Massachusetts, Michigan, New Hampshire, New Jersey, New York, Ohio, Pennsylvania, Rhode I., Vermont, West Virginia, Alabama, Arkansas, Delaware, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, District of Columbia · introduced: Norway, Austria, Belgium, Germany, Hungary, Poland, Switzerland, France, Romania, Yugoslavia, Myanmar · 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 marker40.688, -75.221 · in the densest population, 1079 records (77% 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 1410 georeferenced records inside the native range; the climate across the range on the 1098 of them placed to within 10 km; the map shows only the 563 openly licensed ones, which alone would put the marker 11 km away. 193 records outside the WCVP native range not used. 312 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 1410 in-range records; it decides nothing. Records outside the native range, living specimens and records marked introduced are not used; which records count.

Photographs

Helianthus decapetalus, photograph 1did not loadHelianthus decapetalus, photograph 2did not loadHelianthus decapetalus, photograph 3did not loadHelianthus decapetalus, photograph 4did not loadHelianthus decapetalus, photograph 5did not loadHelianthus decapetalus, photograph 6did not load

Photographs: author not stated, no rights reserved · CC0 (3); (c) Tom Scavo, 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.

Eurybia schreberi Eurybia schreberi Nettle-leaved Michaelmas-daisy Photo: CC BY, Ryan SorrellsElymus riparius Elymus riparius Eastern riverbank wildrye Photo: CC BY, Bryan ConnollyCornus amomum Cornus amomum Silky dogwood Photo: CC BY, Sandy WolkenbergPedicularis canadensis Pedicularis canadensis Early lousewort Photo: CC0, author not statedMicranthes virginiensis Micranthes virginiensis Early saxifrage Photo: CC BY, Hannah JonesViola sororia Viola sororia Woolly blue violet Photo: CC BY, Tanner Barnharst

Other Helianthus 44 in the reference

Helianthus agrestis Helianthus agrestis Rural sunflower Photo: CC BY, sblumenHelianthus angustifolius Helianthus angustifolius Swamp sunflower Photo: CC BY, Sam KieschnickHelianthus annuus Helianthus annuus Sunflower Photo: CC BY, Michelle W. （鍾偉瑋）Helianthus anomalus Helianthus anomalus Sand sunflower Photo: CC BY, Patrick CoxHelianthus argophyllus Helianthus argophyllus Silverleaf sunflower Photo: CC BY, Suanne PyleHelianthus atrorubens Helianthus atrorubens Purple-disk sunflower Photo: CC0, author not statedHelianthus bolanderi Helianthus bolanderi Bolander's sunflower Photo: CC BY, Larry JensenHelianthus californicus Helianthus californicus California sunflower Photo: CC BY, jayjtHelianthus carnosus Helianthus carnosus Fleshy sunflower Photo: CC BY, Brandon CorderHelianthus ciliaris Helianthus ciliaris Texas blueweed Photo: CC BY, Eric KnightHelianthus debilis Helianthus debilis Cucumberleaf sunflower Photo: CC0, author not statedHelianthus deserticola Helianthus deserticola Desert sunflower Photo: CC BY, Matt Berger all 45 ›

Names & registers

Also known as Helianthus decapetalis; Helianthus decapetalus f. frondosus; Helianthus decapetalus var. frondosus; Helianthus decapetalus var. scrophulariifolius; Helianthus dodecapetalus and 9 more. (GBIF Backbone)

Under another author Helianthus strumosus Willd. is an older name of this species, not Helianthus strumosus, a species of the reference. (GBIF Backbone)

GBIFPOWOIPNIWFOWikidataWikipediaiNaturalist

The record

Family
Asteraceae
Described by
L.
Native to
New Brunswick, Ontario, Québec +31
Wild records
1410 in range · 563 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; 55 records within 1 km of a botanic garden, herbarium or zoo left out (37 at a botanic garden or arboretum, 2 at a herbarium, 16 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 43.00_-79.375, lapse-corrected -63 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 105 datasets via GBIF.org; each carries its own licence.

Cultifolio

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