When does saguaro bloom in Arizona?

Most often in May. Across 949 dated, research-grade observations of Carnegiea gigantea in Arizona, the flowering season runs roughly May.

Peak May In flower 949 Examined 5,701 State Arizona

Flowering 949 in flower of 5,701 examined

36%

50%

25%

11%

Proportion of examined Carnegiea gigantea in Arizona in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	2	422	0%	0% to 2%
Feb	0	636	0%	0% to 1%
Mar	14	369	4%	2% to 6%
Apr	131	365	36%	31% to 41%
May	566	1138	50%	47% to 53%
Jun	126	505	25%	21% to 29%
Jul	26	380	7%	5% to 10%
Aug	27	242	11%	8% to 16%
Sep	24	278	9%	6% to 13%
Oct	19	293	6%	4% to 10%
Nov	12	380	3%	2% to 5%
Dec	2	693	0%	0% to 1%

Peak flowering in May. Each bar is the share of Carnegiea gigantea in Arizona 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. 949 of 5,701 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 Arizona found Carnegiea gigantea in flower, not a forecast. It is computed only from observations made in Arizona, 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

Carnegiea gigantea

saguaro

Sourcesevery claim on this page

GBIF (iNaturalist Research-grade Observations). Dated flowering annotations in Arizona. 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.