When does Telegraphweed bloom in California?

Most often in January. Across 1,144 dated, research-grade observations of Heterotheca grandiflora in California, the flowering season runs roughly January to December.

Peak January In flower 1,144 Examined 1,476 State California

Flowering 1,144 in flower of 1,476 examined

90%

82%

76%

72%

57%

33%

57%

70%

90%

83%

89%

83%

Proportion of examined Heterotheca grandiflora in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	135	150	90%	84% to 94%
Feb	84	102	82%	74% to 89%
Mar	79	104	76%	67% to 83%
Apr	56	78	72%	61% to 81%
May	34	60	57%	44% to 68%
Jun	30	91	33%	24% to 43%
Jul	51	90	57%	46% to 66%
Aug	76	109	70%	61% to 78%
Sep	216	240	90%	86% to 93%
Oct	139	168	83%	76% to 88%
Nov	129	145	89%	83% to 93%
Dec	115	139	83%	76% to 88%

Peak flowering in Jan. Each bar is the share of Heterotheca grandiflora 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. 1,144 of 1,476 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 Heterotheca grandiflora 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

Heterotheca grandiflora

Telegraphweed

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.