Hexasepalum radulum(Willd.) Delprete & J.H.Kirkbr.

rough buttonweed

WFO wfo-0001345286 Accepted WFO 2026-06 5 photographs CC0 / CC BY

Plate 1 figs. a–e · 3 observations

This species has been photographed under an open licence only 3 times, so some figures below are different views of the same plant, taken on the same day, rather than different individuals. They are usually different parts of it: the leaf, the flower, the bark.

Hexasepalum radulum, photographed by Kahio Tiberio Mazon
fig. a Kahio Tiberio Mazon, CC0 1.0 / 2018-12-07 / obs. 28933963

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

The specimen a real sheet, in a real collection

Herbarium
The New York Botanical Garden
Accession
397190
Filed as
Diodia radula (Willd.) Cham. & Schltdl.
Det. by
J. Bruza 1981-11-01
Collected
G. Eiten 1961-09-23
Origin
BR
The sheet
View the digitised specimen (CC BY 4.0)

A real pressed plant, in a real collection, under the accession number above. Not an illustration of one. We link to the digitised sheet rather than rehosting it, because the holding institutions do not serve their images to third parties reliably and we are not going to show you a picture we cannot actually deliver. Where we hold no openly licensed sheet for a species this section is simply absent, and where a sheet never recorded who determined it, that field stays empty rather than being filled in. Roughly half of all sheets never recorded a determiner, which is ordinary.

Native range 10 botanical countries

Regions where Hexasepalum radulum is native: Bolivia, Brazil North, Brazil Northeast, Brazil South, Brazil Southeast, Brazil West-Central, Panamá, Paraguay, Peru, Venezuela BoliviaBrazil NorthBrazil NortheastBrazil SouthBrazil SoutheastBrazil West-CentralPanamáParaguayPeruVenezuela
Native distribution of Hexasepalum radulum, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows.
RegionTDWG codeContinent
Bolivia BOL SOUTHERN AMERICA
Brazil North BZN
Brazil Northeast BZE
Brazil South BZS
Brazil Southeast BZL
Brazil West-Central BZC
Panamá PAN
Paraguay PAR
Peru PER
Venezuela VEN

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Where it actually grows measured, from 47 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low 14.2 °C 14.7 °C 18.9 °C
Warmest month, mean daily high 26.0 °C 26.6 °C 27.7 °C
Annual rainfall 1,225 mm 1,739 mm 1,948 mm
Rainfall in the driest quarter 140 mm 302 mm 330 mm

It is not found anywhere that gets close to freezing. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 47 research-grade observations of Hexasepalum radulum that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one.

Also published as 5 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Diodella radula (Willd.) Delprete
  • Diodia muriculata DC.
  • Diodia radula (Willd.) Cham. & Schltdl.
  • Diodia radula subsp. venezuelensis Steyerm.
  • Spermacoce radula Willd.

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. USDA PLANTS Database. common name, checklist symbol DIRA6. public domain. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.