When does California croton bloom in California?

Most often in September. Across 410 dated, research-grade observations of Croton californicus in California, the flowering season runs roughly January to December.

Peak September In flower 410 Examined 524 State California

Flowering 410 in flower of 524 examined

71%

80%

81%

80%

85%

68%

73%

75%

86%

72%

76%

85%

Proportion of examined Croton californicus in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	36	51	71%	57% to 81%
Feb	45	56	80%	68% to 89%
Mar	72	89	81%	72% to 88%
Apr	49	61	80%	69% to 88%
May	50	59	85%	73% to 92%
Jun	28	41	68%	53% to 80%
Jul	16	22	73%	52% to 87%
Aug	18	24	75%	55% to 88%
Sep	19	22	86%	67% to 95%
Oct	23	32	72%	55% to 84%
Nov	25	33	76%	59% to 87%
Dec	29	34	85%	70% to 94%

Peak flowering in Sep. Each bar is the share of Croton 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. 410 of 524 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 Croton 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

Croton californicus

California croton

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.