When does common groundsel bloom in Oregon?

Most often in May. Across 200 dated, research-grade observations of Senecio vulgaris in Oregon, the flowering season runs roughly February to December.

Peak May In flower 200 Examined 239 State Oregon

Flowering 200 in flower of 239 examined

75%

78%

88%

85%

95%

80%

71%

80%

88%

89%

81%

Proportion of examined Senecio vulgaris in Oregon in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	18	24	75%	55% to 88%
Feb	21	27	78%	59% to 89%
Mar	44	50	88%	76% to 94%
Apr	46	54	85%	73% to 92%
May	20	21	95%	77% to 99%
Jun	1	2	too few examined
Jul	4	5	80%	38% to 96%
Aug	5	7	71%	36% to 92%
Sep	4	5	80%	38% to 96%
Oct	7	8	88%	53% to 98%
Nov	8	9	89%	56% to 98%
Dec	22	27	81%	63% to 92%

Peak flowering in May. Each bar is the share of Senecio 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. 200 of 239 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 Oregon found Senecio 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

Senecio vulgaris

common groundsel

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.