When does marsh marigold bloom in Wisconsin?

Most often in May. Across 487 dated, research-grade observations of Caltha palustris in Wisconsin, the flowering season runs roughly April to October.

Peak May In flower 487 Examined 629 State Wisconsin

Flowering 487 in flower of 629 examined

20%

82%

91%

44%

18%

91%

Proportion of examined Caltha palustris in Wisconsin in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	0	too few examined
Feb	0	0	too few examined
Mar	3	15	20%	7% to 45%
Apr	122	149	82%	75% to 87%
May	309	339	91%	88% to 94%
Jun	35	80	44%	33% to 55%
Jul	1	16	6%	1% to 28%
Aug	2	11	18%	5% to 48%
Sep	1	3	too few examined
Oct	10	11	91%	62% to 98%
Nov	4	4	too few examined
Dec	0	1	too few examined

Peak flowering in May. Each bar is the share of Caltha palustris in Wisconsin 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. 487 of 629 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 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 Wisconsin found Caltha palustris in flower, not a forecast. It is computed only from observations made in Wisconsin, 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

Caltha palustris

marsh marigold

Sourcesevery claim on this page

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