When does ragwort bloom in Oregon?

Most often in August. Across 315 dated, research-grade observations of Jacobaea vulgaris in Oregon, the flowering season runs roughly July to September.

Peak August In flower 315 Examined 572 State Oregon

Flowering 315 in flower of 572 examined

35%

10%

50%

92%

74%

55%

36%

47%

Proportion of examined Jacobaea vulgaris in Oregon in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	8	23	35%	19% to 55%
Feb	1	19	5%	1% to 25%
Mar	3	30	10%	3% to 26%
Apr	1	38	3%	0% to 14%
May	5	53	9%	4% to 20%
Jun	30	60	50%	38% to 62%
Jul	101	110	92%	85% to 96%
Aug	79	86	92%	84% to 96%
Sep	40	54	74%	61% to 84%
Oct	22	40	55%	40% to 69%
Nov	9	25	36%	20% to 55%
Dec	16	34	47%	31% to 63%

Peak flowering in Aug. Each bar is the share of Jacobaea vulgaris in Oregon 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. 315 of 572 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 Oregon found Jacobaea vulgaris in flower, not a forecast. It is computed only from observations made in Oregon, 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

Jacobaea vulgaris

ragwort

Sourcesevery claim on this page

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