When does California evening primrose bloom in California?

Most often in July. Across 1,189 dated, research-grade observations of Eulobus californicus in California, the flowering season runs roughly March to July.

Peak July In flower 1,189 Examined 1,583 State California

Flowering 1,189 in flower of 1,583 examined

61%

66%

84%

87%

97%

86%

100%

11%

45%

50%

Proportion of examined Eulobus californicus in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	130	213	61%	54% to 67%
Feb	204	310	66%	60% to 71%
Mar	453	537	84%	81% to 87%
Apr	229	264	87%	82% to 90%
May	68	70	97%	90% to 99%
Jun	25	29	86%	69% to 95%
Jul	9	9	100%	70% to 100%
Aug	2	2	too few examined
Sep	2	4	too few examined
Oct	1	9	11%	2% to 44%
Nov	19	42	45%	31% to 60%
Dec	47	94	50%	40% to 60%

Peak flowering in Jul. Each bar is the share of Eulobus californicus 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. 1,189 of 1,583 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 2 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 California found Eulobus californicus 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

Eulobus californicus

California evening primrose

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.