When does Red Clover bloom in Massachusetts?

Most often in September. Across 408 dated, research-grade observations of Trifolium pratense in Massachusetts, the flowering season runs roughly May to November.

Peak September In flower 408 Examined 442 State Massachusetts

Flowering 408 in flower of 442 examined

85%

98%

96%

100%

88%

87%

Proportion of examined Trifolium pratense in Massachusetts in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	1	too few examined
Feb	0	0	too few examined
Mar	0	0	too few examined
Apr	0	10	0%	0% to 28%
May	55	65	85%	74% to 91%
Jun	124	126	98%	94% to 100%
Jul	47	48	98%	89% to 100%
Aug	46	48	96%	86% to 99%
Sep	86	86	100%	96% to 100%
Oct	36	41	88%	74% to 95%
Nov	13	15	87%	62% to 96%
Dec	1	2	too few examined

Peak flowering in Sep. Each bar is the share of Trifolium pratense in Massachusetts 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. 408 of 442 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 Massachusetts found Trifolium pratense in flower, not a forecast. It is computed only from observations made in Massachusetts, 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

Trifolium pratense

Red Clover

Sourcesevery claim on this page

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