When does buttonbush bloom in Oklahoma?

Most often in July. Across 292 dated, research-grade observations of Cephalanthus occidentalis in Oklahoma, the flowering season runs roughly June to July.

Peak July In flower 292 Examined 710 State Oklahoma

Flowering 292 in flower of 710 examined

13%

81%

85%

59%

23%

Proportion of examined Cephalanthus occidentalis in Oklahoma in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	31	0%	0% to 11%
Feb	0	9	0%	0% to 30%
Mar	0	9	0%	0% to 30%
Apr	1	25	4%	1% to 20%
May	2	16	13%	4% to 36%
Jun	75	93	81%	71% to 87%
Jul	107	126	85%	78% to 90%
Aug	78	133	59%	50% to 67%
Sep	27	118	23%	16% to 31%
Oct	2	108	2%	1% to 7%
Nov	0	21	0%	0% to 15%
Dec	0	21	0%	0% to 15%

Peak flowering in Jul. Each bar is the share of Cephalanthus occidentalis in Oklahoma 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. 292 of 710 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 Oklahoma found Cephalanthus occidentalis in flower, not a forecast. It is computed only from observations made in Oklahoma, 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

Cephalanthus occidentalis

buttonbush

Sourcesevery claim on this page

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