When does poison hemlock bloom in Arkansas?

Most often in June. Across 72 dated, research-grade observations of Conium maculatum in Arkansas, the flowering season runs roughly May to June.

Peak June In flower 72 Examined 149 State Arkansas

Flowering 72 in flower of 149 examined

16%

81%

84%

Proportion of examined Conium maculatum in Arkansas in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	2	too few examined
Feb	0	6	0%	0% to 39%
Mar	0	21	0%	0% to 15%
Apr	5	32	16%	7% to 32%
May	51	63	81%	70% to 89%
Jun	16	19	84%	62% to 94%
Jul	0	0	too few examined
Aug	0	1	too few examined
Sep	0	0	too few examined
Oct	0	1	too few examined
Nov	0	3	too few examined
Dec	0	1	too few examined

Peak flowering in Jun. Each bar is the share of Conium maculatum in Arkansas 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. 72 of 149 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 Arkansas found Conium maculatum in flower, not a forecast. It is computed only from observations made in Arkansas, 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

Conium maculatum

poison hemlock

Sourcesevery claim on this page

GBIF (iNaturalist Research-grade Observations). Dated flowering annotations in Arkansas. 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.