When does great rhododendron bloom in North Carolina?

Most often in July. Across 357 dated, research-grade observations of Rhododendron maximum in North Carolina, the flowering season runs roughly June to August.

Peak July In flower 357 Examined 495 State North Carolina

Flowering 357 in flower of 495 examined

18%

86%

94%

81%

14%

Proportion of examined Rhododendron maximum in North Carolina in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	5	0%	0% to 43%
Feb	0	9	0%	0% to 30%
Mar	1	18	6%	1% to 26%
Apr	1	12	8%	1% to 35%
May	2	11	18%	5% to 48%
Jun	120	139	86%	80% to 91%
Jul	209	222	94%	90% to 97%
Aug	21	26	81%	62% to 91%
Sep	2	14	14%	4% to 40%
Oct	1	21	5%	1% to 23%
Nov	0	6	0%	0% to 39%
Dec	0	12	0%	0% to 24%

Peak flowering in Jul. Each bar is the share of Rhododendron maximum in North Carolina 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. 357 of 495 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 North Carolina found Rhododendron maximum in flower, not a forecast. It is computed only from observations made in North Carolina, 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

Rhododendron maximum

great rhododendron

Sourcesevery claim on this page

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