When does Orcutt's aster bloom in California?

Most often in April. Across 601 dated, research-grade observations of Xylorhiza orcuttii in California, the flowering season runs roughly March to December.

Peak April In flower 601 Examined 859 State California

Flowering 601 in flower of 859 examined

76%

63%

88%

98%

86%

59%

26%

87%

Proportion of examined Xylorhiza orcuttii in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	131	172	76%	69% to 82%
Feb	200	318	63%	57% to 68%
Mar	115	131	88%	81% to 92%
Apr	41	42	98%	88% to 100%
May	6	7	86%	49% to 97%
Jun	0	0	too few examined
Jul	0	0	too few examined
Aug	0	0	too few examined
Sep	1	1	too few examined
Oct	17	29	59%	41% to 74%
Nov	21	80	26%	18% to 37%
Dec	69	79	87%	78% to 93%

Peak flowering in Apr. Each bar is the share of Xylorhiza orcuttii 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. 601 of 859 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 4 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 Xylorhiza orcuttii 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

Xylorhiza orcuttii

Orcutt's aster

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.