When does groundsel tree bloom in New Jersey?

Most often in September. Across 105 dated, research-grade observations of Baccharis halimifolia in New Jersey, the flowering season runs roughly September.

Peak September In flower 105 Examined 246 State New Jersey

Flowering 105 in flower of 246 examined

65%

51%

13%

Proportion of examined Baccharis halimifolia in New Jersey in flower, by month
Month	In flower	Examined	Share	95% interval
Jan	0	6	0%	0% to 39%
Feb	0	0	too few examined
Mar	0	1	too few examined
Apr	0	3	too few examined
May	0	2	too few examined
Jun	0	9	0%	0% to 30%
Jul	0	4	too few examined
Aug	0	15	0%	0% to 20%
Sep	64	99	65%	55% to 73%
Oct	39	77	51%	40% to 62%
Nov	1	22	5%	1% to 22%
Dec	1	8	13%	2% to 47%

Peak flowering in Sep. Each bar is the share of Baccharis halimifolia 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. 105 of 246 examined observations were in flower, every one of them research grade. The whisker on each bar is a 95% Wilson interval. 5 months have fewer than 5 examined observations, so no proportion is drawn for them. 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 Baccharis halimifolia 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

Baccharis halimifolia

groundsel tree

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.