Bupleurum americanum (American thorow wax)

Plate 1 figs. a–h · 8 separate observations

Bupleurum americanum, photographed by Matt Berger — fig. a Matt Berger, CC BY 4.0 / 2021-07-04 / obs. 141190310

Bupleurum americanum, photographed by Syd Cannings — fig. b Syd Cannings, CC BY 4.0 / obs. 139958870

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.

Native range 11 botanical countries

Native distribution of Bupleurum americanum, 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.

Region	TDWG code	Continent
Alaska	ASK	NORTHERN AMERICA
Alberta	ABT
Colorado	COL
Idaho	IDA
Montana	MNT
New Mexico	NWM
Northwest Territories	NWT
Oregon	ORE
Wyoming	WYO
Yukon	YUK
Magadan	MAG	ASIA-TEMPERATE

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.

Flowering 41 in flower of 44 examined

87%

100%

86%

Proportion of examined Bupleurum americanum in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	0	too few examined
Feb	0	0	too few examined
Mar	0	0	too few examined
Apr	0	0	too few examined
May	1	1	too few examined
Jun	13	15	87%	62% to 96%
Jul	20	20	100%	84% to 100%
Aug	6	7	86%	49% to 97%
Sep	1	1	too few examined
Oct	0	0	too few examined
Nov	0	0	too few examined
Dec	0	0	too few examined

Peak flowering in Jul. Each bar is the share of Bupleurum americanum observations in which someone actually recorded the reproductive state and found the plant in flower, not the raw number of flowering records. That distinction matters: people observe plants far more in spring than in winter, so a bare count of flowering records partly measures when people go outside. Dividing by the number examined removes that. 41 of 44 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 9 months have fewer than 5 examined observations, so no proportion is drawn for them. This is still a global aggregate and not a forecast for your garden: the same species flowers on different dates in different hemispheres. Where a species has fewer than 30 flowering records we do not draw this chart at all. Computed from 10.15468/dl.cgje2x.

Also published as 9 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.

Bupleurum arcticum Koso-Pol.
Bupleurum arcticum (Regel) Krasnob.
Bupleurum ranunculoides f. arcticum (Regel) H.Wolff
Bupleurum ranunculoides var. arcticum Regel
Bupleurum sibiricum subsp. americanum (J.M.Coult. & Rose) Krasnob.
Bupleurum triradiatum subsp. arcticum (Regel & Tiling) Hultén
Bupleurum triradiatum var. adamsii Koso-Pol.
Bupleurum triradiatum var. arcticum (Regel & Tiling) Koso-Pol.
Bupleurum triradiatum var. humilis Rupr. ex Koso-Pol.

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.
Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
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.