Oenothera triloba (Stemless Evening Primrose)

Plate 1 figs. a–h

Oenothera triloba, photographed by Victor Engel — fig. a Victor Engel, CC BY 4.0 / 2022-03-14 / obs. 182950073

Oenothera triloba, photographed by Reid Hardin — fig. b Reid Hardin, CC BY 4.0 / obs. 117578823

Oenothera triloba, photographed by Meghan Cassidy — fig. c Meghan Cassidy, CC BY-SA 4.0 / obs. 125852603

Oenothera triloba, photographed by saltyhiker — fig. e saltyhiker, CC BY 4.0 / obs. 185696042

Oenothera triloba, photographed by Annika Lindqvist — fig. g Annika Lindqvist, CC BY 4.0 / obs. 194370164

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.

Flowering n = 409 observations

225

Flowering observations of Oenothera triloba by month
Month	Observations
Jan	3
Feb	70
Mar	225
Apr	81
May	22
Jun	3
Jul	1
Aug	1
Sep	0
Oct	2
Nov	0
Dec	1

Peak flowering in Mar, from 409 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 8 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.

Lavauxia nuttalliana Spach
Lavauxia triloba (Nutt.) Bartl.
Lavauxia triloba var. watsonii Britton
Lavauxia watsonii Small
Oenothera rhizocarpa Spreng.
Oenothera roemeriana Scheele
Oenothera triloba var. parviflora S.Watson
Oenothera triloba var. watsonii F.C.Gates

Sourcesevery claim on this page

World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
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.