When does common boneset bloom in Indiana?

Most often in September. Across 99 dated, research-grade observations of Eupatorium perfoliatum in Indiana, the flowering season runs roughly September.

Peak September In flower 99 Examined 153 State Indiana

Flowering 99 in flower of 153 examined

39%

74%

97%

36%

Proportion of examined Eupatorium perfoliatum in Indiana 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	0	3	too few examined
Jun	0	10	0%	0% to 28%
Jul	9	23	39%	22% to 59%
Aug	51	69	74%	62% to 83%
Sep	35	36	97%	86% to 100%
Oct	4	11	36%	15% to 65%
Nov	0	1	too few examined
Dec	0	0	too few examined

Peak flowering in Sep. Each bar is the share of Eupatorium perfoliatum in Indiana 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. 99 of 153 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 7 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.wt38fd.

What this is, and what it is not

This is a record of when people in Indiana found Eupatorium perfoliatum in flower, not a forecast. It is computed only from observations made in Indiana, so it is not the species’ global average dragged onto a map: the same plant flowers on different dates in different places, and that is the entire point of the page.

It will not tell you what your particular plant will do this year. Bloom time moves with the season, with altitude, and with the weather, and a warm February pulls everything forward. We publish the distribution and the sample size, and we refuse to draw a month that too few people examined.

The plant

Eupatorium perfoliatum

common boneset

Sourcesevery claim on this page

GBIF (iNaturalist Research-grade Observations). Dated flowering annotations in Indiana. Every record achieved iNaturalist quality grade Research, which is applied upstream at export. 10.15468/dl.wt38fd. Retrieved 2026-07-14.
World Flora Online Plant List. The accepted name. CC0. Retrieved 2026-07-12.