When does common hibiscus bloom in New York?

Most often in August. Across 161 dated, research-grade observations of Hibiscus syriacus in New York, the flowering season runs roughly July to September.

Peak August In flower 161 Examined 270 State New York

Flowering 161 in flower of 270 examined

18%

77%

91%

79%

21%

Proportion of examined Hibiscus syriacus in New York in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	3	too few examined
Feb	0	2	too few examined
Mar	0	1	too few examined
Apr	1	12	8%	1% to 35%
May	0	21	0%	0% to 15%
Jun	2	11	18%	5% to 48%
Jul	58	75	77%	67% to 85%
Aug	59	65	91%	81% to 96%
Sep	38	48	79%	66% to 88%
Oct	3	14	21%	8% to 48%
Nov	0	9	0%	0% to 30%
Dec	0	9	0%	0% to 30%

Peak flowering in Aug. Each bar is the share of Hibiscus syriacus in New York 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. 161 of 270 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 3 months have fewer than 5 examined observations, so no proportion is drawn for them. 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 New York found Hibiscus syriacus in flower, not a forecast. It is computed only from observations made in New York, 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

Hibiscus syriacus

common hibiscus

Sourcesevery claim on this page

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