When does Aquatic Milkweed bloom in Florida?

Most often in August. Across 129 dated, research-grade observations of Asclepias perennis in Florida, the flowering season runs roughly March to October.

Peak August In flower 129 Examined 159 State Florida

Flowering 129 in flower of 159 examined

14%

83%

92%

95%

90%

95%

96%

93%

83%

10%

Proportion of examined Asclepias perennis in Florida in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	1	7	14%	3% to 51%
Feb	0	5	0%	0% to 43%
Mar	5	6	83%	44% to 97%
Apr	12	13	92%	67% to 99%
May	20	21	95%	77% to 99%
Jun	19	21	90%	71% to 97%
Jul	21	22	95%	78% to 99%
Aug	22	23	96%	79% to 99%
Sep	14	15	93%	70% to 99%
Oct	10	12	83%	55% to 95%
Nov	4	4	too few examined
Dec	1	10	10%	2% to 40%

Peak flowering in Aug. Each bar is the share of Asclepias perennis in Florida 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. 129 of 159 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 Florida found Asclepias perennis in flower, not a forecast. It is computed only from observations made in Florida, 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

Asclepias perennis

Aquatic Milkweed

Sourcesevery claim on this page

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