When does hemp dogbane bloom in New Jersey?

Most often in July. Across 87 dated, research-grade observations of Apocynum cannabinum in New Jersey, the flowering season runs roughly June to July.

Peak July In flower 87 Examined 242 State New Jersey

Flowering 87 in flower of 242 examined

59%

70%

44%

Proportion of examined Apocynum cannabinum in New Jersey in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	5	0%	0% to 43%
Feb	0	6	0%	0% to 39%
Mar	0	7	0%	0% to 35%
Apr	0	4	too few examined
May	1	15	7%	1% to 30%
Jun	38	64	59%	47% to 71%
Jul	33	47	70%	56% to 81%
Aug	15	34	44%	29% to 61%
Sep	0	19	0%	0% to 17%
Oct	0	19	0%	0% to 17%
Nov	0	12	0%	0% to 24%
Dec	0	10	0%	0% to 28%

Peak flowering in Jul. Each bar is the share of Apocynum cannabinum in New Jersey 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. 87 of 242 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. One month has fewer than 5 examined observations, so no proportion is drawn for it. 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 New Jersey found Apocynum cannabinum in flower, not a forecast. It is computed only from observations made in New Jersey, 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 New Jersey. 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.