When does California flannelbush bloom in California?

Most often in June. Across 290 dated, research-grade observations of Fremontodendron californicum in California, the flowering season runs roughly January to June.

Peak June In flower 290 Examined 385 State California

Flowering 290 in flower of 385 examined

74%

71%

70%

84%

89%

90%

66%

14%

33%

27%

Proportion of examined Fremontodendron californicum in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	14	19	74%	51% to 88%
Feb	5	7	71%	36% to 92%
Mar	16	23	70%	49% to 84%
Apr	46	55	84%	72% to 91%
May	100	112	89%	82% to 94%
Jun	80	89	90%	82% to 95%
Jul	21	32	66%	48% to 80%
Aug	2	14	14%	4% to 40%
Sep	0	6	0%	0% to 39%
Oct	1	11	9%	2% to 38%
Nov	2	6	33%	10% to 70%
Dec	3	11	27%	10% to 57%

Peak flowering in Jun. Each bar is the share of Fremontodendron californicum 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. 290 of 385 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 Fremontodendron californicum 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

Fremontodendron californicum

California flannelbush

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.