When does Alligatorweed bloom in Mississippi?

Most often in May. Across 101 dated, research-grade observations of Alternanthera philoxeroides in Mississippi, the flowering season runs roughly April to September.

Peak May In flower 101 Examined 149 State Mississippi

Flowering 101 in flower of 149 examined

44%

76%

79%

76%

70%

67%

17%

Proportion of examined Alternanthera philoxeroides in Mississippi in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	7	0%	0% to 35%
Feb	0	0	too few examined
Mar	4	9	44%	19% to 73%
Apr	19	25	76%	57% to 89%
May	26	33	79%	62% to 89%
Jun	34	45	76%	61% to 86%
Jul	7	10	70%	40% to 89%
Aug	2	3	too few examined
Sep	4	6	67%	30% to 90%
Oct	1	2	too few examined
Nov	3	3	too few examined
Dec	1	6	17%	3% to 56%

Peak flowering in May. Each bar is the share of Alternanthera philoxeroides in Mississippi 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. 101 of 149 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 Mississippi found Alternanthera philoxeroides in flower, not a forecast. It is computed only from observations made in Mississippi, 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

Alternanthera philoxeroides

Alligatorweed

Sourcesevery claim on this page

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