When does Japanese barberry bloom in New York?

Most often in April. Across 102 dated, research-grade observations of Berberis thunbergii in New York, the flowering season runs roughly April to May.

Peak April In flower 102 Examined 759 State New York

Flowering 102 in flower of 759 examined

38%

Proportion of examined Berberis thunbergii in New York in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	27	0%	0% to 12%
Feb	0	18	0%	0% to 18%
Mar	0	22	0%	0% to 15%
Apr	55	143	38%	31% to 47%
May	44	116	38%	30% to 47%
Jun	2	56	4%	1% to 12%
Jul	0	24	0%	0% to 14%
Aug	0	37	0%	0% to 9%
Sep	0	73	0%	0% to 5%
Oct	0	153	0%	0% to 2%
Nov	1	59	2%	0% to 9%
Dec	0	31	0%	0% to 11%

Peak flowering in Apr. Each bar is the share of Berberis thunbergii 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. 102 of 759 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 New York found Berberis thunbergii 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

Berberis thunbergii

Japanese barberry

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.