When does common yarrow bloom in New Jersey?

Most often in July. Across 150 dated, research-grade observations of Achillea millefolium in New Jersey, the flowering season runs roughly June to July.

Peak July In flower 150 Examined 281 State New Jersey

Flowering 150 in flower of 281 examined

14%

80%

93%

72%

36%

24%

18%

Proportion of examined Achillea millefolium in New Jersey in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	5	0%	0% to 43%
Feb	0	1	too few examined
Mar	0	7	0%	0% to 35%
Apr	1	24	4%	1% to 20%
May	4	28	14%	6% to 31%
Jun	75	94	80%	71% to 87%
Jul	42	45	93%	82% to 98%
Aug	13	18	72%	49% to 88%
Sep	8	22	36%	20% to 57%
Oct	5	21	24%	11% to 45%
Nov	2	11	18%	5% to 48%
Dec	0	5	0%	0% to 43%

Peak flowering in Jul. Each bar is the share of Achillea millefolium in New Jersey 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. 150 of 281 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. One month has fewer than 5 examined observations, so no proportion is drawn for it. 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 Jersey found Achillea millefolium in flower, not a forecast. It is computed only from observations made in New Jersey, 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

Achillea millefolium

common yarrow

Sourcesevery claim on this page

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