Houstonia caeruleaL.

azure bluet

WFO wfo-0000215160 Accepted WFO 2026-06 8 photographs CC0 / CC BY

Plate 1 figs. a–h

Houstonia caerulea, photographed by Ryan Sorrells
fig. a Ryan Sorrells, CC BY 4.0 / 2022-06-11 / obs. 205674120
Houstonia caerulea, photographed by Mary E. Macaulay, P.Eng.
fig. b Mary E. Macaulay, P.Eng., CC BY 4.0 / obs. 204522320
Houstonia caerulea, photographed by Clay Gibbons
fig. c Clay Gibbons, CC BY 4.0 / obs. 201759249
Houstonia caerulea, photographed by Bex Goreham
fig. d Bex Goreham, CC BY 4.0 / obs. 203733016
Houstonia caerulea, photographed by Nick Kleinschmidt
fig. e Nick Kleinschmidt, CC BY 4.0 / obs. 202841876
Houstonia caerulea, photographed by Mary E. Macaulay, P.Eng.
fig. f Mary E. Macaulay, P.Eng., CC BY 4.0 / obs. 204520860
Houstonia caerulea, photographed by Thomas J Nolan
fig. g Thomas J Nolan, CC BY 4.0 / obs. 201079953
Houstonia caerulea, photographed by Tom Armstrong
fig. h Tom Armstrong, CC BY 4.0 / obs. 201343853

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.

Confused withby our own model

These are not lookalikes we guessed at. Each one is a species our identification model genuinely mistook for this plant, and how many times. The error rate is published.

Flowering n = 13,621 observations

Peak flowering in May, from 13,621 community-annotated observations worldwide. This is a global aggregate, not a forecast for your garden: the same species flowers on different dates in different hemispheres, and citizen-science records cluster near cities, at weekends, and in spring. Where a species has fewer than 30 annotated records we do not draw this chart at all.

Also published as 23 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.

  • Anotis coerulea (L.) G.Don
  • Anotis gentianoides (Endl.) Walp.
  • Hedyotis brachiata Miq. ex Hook.f.
  • Hedyotis caerulea (L.) Hook.
  • Hedyotis caerulea f. albiflora (Millsp.) Fosberg
  • Hedyotis caerulea f. benkei Fosberg
  • Hedyotis caerulea var. faxonorum (Pease & A.H.Moore) Fosberg
  • Hedyotis gentianoides Endl.
  • Houstonia caerulea f. albiflora Millsp.
  • Houstonia caerulea f. caerulea
  • Houstonia caerulea var. caerulea
  • Houstonia caerulea var. elatior (Michx.) Pursh
  • Houstonia caerulea var. faxonorum Pease & A.H.Moore
  • Houstonia caerulea var. piersii Barbour
  • Houstonia caerulea var. toxonorum Stevens
  • Houstonia faxonorum (Pease & A.H.Moore) Fernald
  • Houstonia grandiflora Raf.
  • Houstonia linnaei Michx.
  • Houstonia linnaei var. elatior Michx.
  • Houstonia pusilla J.F.Gmel.
  • Houstonia serpyllifolia Graham
  • Oldenlandia caerulea (L.) A.Gray
  • Poiretia erecta J.F.Gmel.

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.

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