When does hemp dogbane bloom in Indiana?

Most often in June. Across 61 dated, research-grade observations of Apocynum cannabinum in Indiana, the flowering season runs roughly May to August.

Peak June In flower 61 Examined 111 State Indiana

Flowering 61 in flower of 111 examined

67%

78%

74%

70%

Proportion of examined Apocynum cannabinum in Indiana in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	0	too few examined
Feb	0	5	0%	0% to 43%
Mar	0	5	0%	0% to 43%
Apr	0	4	too few examined
May	6	9	67%	35% to 88%
Jun	28	36	78%	62% to 88%
Jul	20	27	74%	55% to 87%
Aug	7	10	70%	40% to 89%
Sep	0	5	0%	0% to 43%
Oct	0	8	0%	0% to 32%
Nov	0	1	too few examined
Dec	0	1	too few examined

Peak flowering in Jun. Each bar is the share of Apocynum cannabinum 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. 61 of 111 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 4 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 Apocynum cannabinum 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

Apocynum cannabinum

hemp dogbane

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.