When does western blue-eyed grass bloom in California?

Most often in April. Across 4,066 dated, research-grade observations of Sisyrinchium bellum in California, the flowering season runs roughly February to November.

Peak April In flower 4,066 Examined 4,241 State California

Flowering 4,066 in flower of 4,241 examined

65%

85%

97%

98%

97%

93%

95%

81%

78%

89%

58%

Proportion of examined Sisyrinchium bellum in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	31	48	65%	50% to 77%
Feb	150	176	85%	79% to 90%
Mar	932	964	97%	95% to 98%
Apr	1652	1680	98%	98% to 99%
May	722	739	98%	96% to 99%
Jun	264	272	97%	94% to 99%
Jul	126	135	93%	88% to 96%
Aug	86	91	95%	88% to 98%
Sep	42	52	81%	68% to 89%
Oct	25	32	78%	61% to 89%
Nov	17	19	89%	69% to 97%
Dec	19	33	58%	41% to 73%

Peak flowering in Apr. Each bar is the share of Sisyrinchium bellum in California 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. 4,066 of 4,241 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 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 California found Sisyrinchium bellum in flower, not a forecast. It is computed only from observations made in California, 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

Sisyrinchium bellum

western blue-eyed grass

Sourcesevery claim on this page

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