When does western vervain bloom in California?

Most often in June. Across 589 dated, research-grade observations of Verbena lasiostachys in California, the flowering season runs roughly April to November.

Peak June In flower 589 Examined 620 State California

Flowering 589 in flower of 620 examined

60%

61%

86%

97%

100%

99%

98%

97%

91%

85%

Proportion of examined Verbena lasiostachys in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	2	3	too few examined
Feb	6	10	60%	31% to 83%
Mar	11	18	61%	39% to 80%
Apr	51	59	86%	75% to 93%
May	147	151	97%	93% to 99%
Jun	168	168	100%	98% to 100%
Jul	91	92	99%	94% to 100%
Aug	43	44	98%	88% to 100%
Sep	35	36	97%	86% to 100%
Oct	20	22	91%	72% to 97%
Nov	11	13	85%	58% to 96%
Dec	4	4	too few examined

Peak flowering in Jun. Each bar is the share of Verbena lasiostachys 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. 589 of 620 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 Verbena lasiostachys 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

Verbena lasiostachys

western vervain

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.