When does desert thorn-apple bloom in California?

Most often in October. Across 614 dated, research-grade observations of Datura discolor in California, the flowering season runs roughly October to November.

Peak October In flower 614 Examined 1,156 State California

Flowering 614 in flower of 1,156 examined

43%

45%

44%

36%

14%

33%

85%

77%

59%

Proportion of examined Datura discolor in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	85	198	43%	36% to 50%
Feb	105	234	45%	39% to 51%
Mar	97	222	44%	37% to 50%
Apr	18	50	36%	24% to 50%
May	1	7	14%	3% to 51%
Jun	0	5	0%	0% to 43%
Jul	0	1	too few examined
Aug	0	0	too few examined
Sep	3	9	33%	12% to 65%
Oct	51	60	85%	74% to 92%
Nov	152	197	77%	71% to 82%
Dec	102	173	59%	52% to 66%

Peak flowering in Oct. Each bar is the share of Datura discolor 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. 614 of 1,156 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 Datura discolor 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

Datura discolor

desert thorn-apple

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.