When does French broom bloom in California?

Most often in April. Across 870 dated, research-grade observations of Genista monspessulana in California, the flowering season runs roughly February to May.

Peak April In flower 870 Examined 1,166 State California

Flowering 870 in flower of 1,166 examined

57%

87%

94%

85%

54%

31%

38%

33%

39%

43%

56%

Proportion of examined Genista monspessulana in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	29	51	57%	43% to 70%
Feb	101	116	87%	80% to 92%
Mar	189	201	94%	90% to 97%
Apr	280	297	94%	91% to 96%
May	119	140	85%	78% to 90%
Jun	44	81	54%	44% to 65%
Jul	16	52	31%	20% to 44%
Aug	21	55	38%	27% to 51%
Sep	18	55	33%	22% to 46%
Oct	21	54	39%	27% to 52%
Nov	12	28	43%	27% to 61%
Dec	20	36	56%	40% to 70%

Peak flowering in Apr. Each bar is the share of Genista monspessulana 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. 870 of 1,166 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 Genista monspessulana 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

Genista monspessulana

French broom

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.