When does ribwort plantain bloom in California?

Most often in May. Across 689 dated, research-grade observations of Plantago lanceolata in California, the flowering season runs roughly March to August.

Peak May In flower 689 Examined 901 State California

Flowering 689 in flower of 901 examined

57%

62%

75%

82%

90%

89%

72%

81%

70%

58%

40%

13%

Proportion of examined Plantago lanceolata in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	26	46	57%	42% to 70%
Feb	44	71	62%	50% to 72%
Mar	110	146	75%	68% to 82%
Apr	240	294	82%	77% to 86%
May	136	151	90%	84% to 94%
Jun	62	70	89%	79% to 94%
Jul	18	25	72%	52% to 86%
Aug	13	16	81%	57% to 93%
Sep	16	23	70%	49% to 84%
Oct	14	24	58%	39% to 76%
Nov	8	20	40%	22% to 61%
Dec	2	15	13%	4% to 38%

Peak flowering in May. Each bar is the share of Plantago lanceolata 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. 689 of 901 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 Plantago lanceolata 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

Plantago lanceolata

ribwort plantain

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.