When does bird's-foot trefoil bloom in Massachusetts?

Most often in June. Across 303 dated, research-grade observations of Lotus corniculatus in Massachusetts, the flowering season runs roughly May to September.

Peak June In flower 303 Examined 312 State Massachusetts

Flowering 303 in flower of 312 examined

82%

100%

99%

98%

95%

Proportion of examined Lotus corniculatus in Massachusetts in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	0	too few examined
Feb	0	0	too few examined
Mar	0	0	too few examined
Apr	0	2	too few examined
May	14	17	82%	59% to 94%
Jun	134	134	100%	97% to 100%
Jul	91	92	99%	94% to 100%
Aug	46	47	98%	89% to 100%
Sep	18	19	95%	75% to 99%
Oct	0	1	too few examined
Nov	0	0	too few examined
Dec	0	0	too few examined

Peak flowering in Jun. Each bar is the share of Lotus corniculatus 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. 303 of 312 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 Massachusetts found Lotus corniculatus 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

Lotus corniculatus

bird's-foot trefoil

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.