When does scarlet monkeyflower bloom in California?

Most often in September. Across 1,518 dated, research-grade observations of Erythranthe cardinalis in California, the flowering season runs roughly June to November.

Peak September In flower 1,518 Examined 1,630 State California

Flowering 1,518 in flower of 1,630 examined

56%

44%

48%

71%

95%

98%

99%

92%

86%

74%

Proportion of examined Erythranthe cardinalis in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	5	9	56%	27% to 81%
Feb	2	4	too few examined
Mar	4	9	44%	19% to 73%
Apr	10	21	48%	28% to 68%
May	79	111	71%	62% to 79%
Jun	360	379	95%	92% to 97%
Jul	391	400	98%	96% to 99%
Aug	315	323	98%	95% to 99%
Sep	211	214	99%	96% to 100%
Oct	85	92	92%	85% to 96%
Nov	42	49	86%	73% to 93%
Dec	14	19	74%	51% to 88%

Peak flowering in Sep. Each bar is the share of Erythranthe cardinalis 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. 1,518 of 1,630 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. One month has fewer than 5 examined observations, so no proportion is drawn for it. 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 Erythranthe cardinalis 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

Erythranthe cardinalis

scarlet monkeyflower

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.