When does garden nasturtium bloom in California?

Most often in June. Across 542 dated, research-grade observations of Tropaeolum majus in California, the flowering season runs roughly April to October.

Peak June In flower 542 Examined 621 State California

Flowering 542 in flower of 621 examined

61%

69%

96%

94%

100%

97%

81%

63%

43%

Proportion of examined Tropaeolum majus in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	14	23	61%	41% to 78%
Feb	17	28	61%	42% to 76%
Mar	37	54	69%	55% to 79%
Apr	140	146	96%	91% to 98%
May	102	108	94%	88% to 97%
Jun	71	71	100%	95% to 100%
Jul	51	51	100%	93% to 100%
Aug	25	25	100%	87% to 100%
Sep	38	39	97%	87% to 100%
Oct	17	21	81%	60% to 92%
Nov	20	32	63%	45% to 77%
Dec	10	23	43%	26% to 63%

Peak flowering in Jun. Each bar is the share of Tropaeolum majus 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. 542 of 621 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 Tropaeolum majus 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

Tropaeolum majus

garden nasturtium

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.