When does Japanese honeysuckle bloom in Pennsylvania?

Most often in August. Across 168 dated, research-grade observations of Lonicera japonica in Pennsylvania, the flowering season runs roughly June to August.

Peak August In flower 168 Examined 368 State Pennsylvania

Flowering 168 in flower of 368 examined

69%

85%

82%

100%

60%

21%

Proportion of examined Lonicera japonica in Pennsylvania in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	13	0%	0% to 23%
Feb	0	6	0%	0% to 39%
Mar	0	17	0%	0% to 18%
Apr	0	13	0%	0% to 23%
May	24	35	69%	52% to 81%
Jun	75	88	85%	76% to 91%
Jul	18	22	82%	61% to 93%
Aug	13	13	100%	77% to 100%
Sep	25	42	60%	44% to 73%
Oct	9	42	21%	12% to 36%
Nov	4	54	7%	3% to 18%
Dec	0	23	0%	0% to 14%

Peak flowering in Aug. Each bar is the share of Lonicera japonica in Pennsylvania 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. 168 of 368 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 Pennsylvania found Lonicera japonica in flower, not a forecast. It is computed only from observations made in Pennsylvania, 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

Lonicera japonica

Japanese honeysuckle

Sourcesevery claim on this page

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