When does Tree Mallow bloom in California?

Most often in May. Across 629 dated, research-grade observations of Malva arborea in California, the flowering season runs roughly March to September.

Peak May In flower 629 Examined 720 State California

Flowering 629 in flower of 720 examined

68%

75%

84%

94%

97%

93%

94%

92%

82%

58%

72%

54%

Proportion of examined Malva arborea in California in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	13	19	68%	46% to 85%
Feb	18	24	75%	55% to 88%
Mar	53	63	84%	73% to 91%
Apr	105	112	94%	88% to 97%
May	106	109	97%	92% to 99%
Jun	117	126	93%	87% to 96%
Jul	67	71	94%	86% to 98%
Aug	59	64	92%	83% to 97%
Sep	41	50	82%	69% to 90%
Oct	19	33	58%	41% to 73%
Nov	18	25	72%	52% to 86%
Dec	13	24	54%	35% to 72%

Peak flowering in May. Each bar is the share of Malva arborea 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. 629 of 720 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 Malva arborea 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

Malva arborea

Tree Mallow

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.