Wildflowers of the United States

Butterweed, Yellowtop, Cressleaf Groundsel, Floodplain Ragwort - Packera glabella

Genus Common Name: Ragwort

Native Status: Native

Dicot Annual Herb

Packera glabella - Butterweed, Yellowtop, Cressleaf Groundsel, Floodplain Ragwort. Packera was separated from the Senecio genus and contains what were categorized as the aureoid senecios (I assume this means "golden ragworts") by Asa Gray. The separation was partially based on genetic studies.

There are 64 species of Packera recognized worldwide as of this writing (April 2012), over 50 of which are found in the United States. More than half of the species are glabrous (without hairs) or mostly glabrous, having hairs only in the joints - axils of leaves, and the bases of the flower heads and stems. The epithet for this species, glabella, references the usuallyy glabrous nature of the plant, although it may occasionally have a few hairs in the leaf axils. Packera glabella is found in damp to quite wet soils.

The genus is named for Canadian botanist John G. Packer, the author of Flora of Alberta and Professor Emeritus at the University of Alberta.

It is a weedy plant, and is classified as a Prohibited noxious weed in Ohio

Found in:
AL, AR, FL, GA, IA, IL, IN, KS, KY, LA, MD, MO, MS, NC, NE, OH, OK, SC, SD, TN, TX

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Distribution of Packera glabella in the United States and Canada:

Map courtesy of The Biota of North America Program.
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Site: Walker County, GA Date: 2012-April-02	Photographer: Gerald C. Williamson Nikon D7000 Tamron SP 90MM f/2.8 AF Macro
Butterweed usually 13 yellow ray florets, but may have as few as 8. There may be 50 or more yellow disc florets. A somewhat early spring flower, they can be found blooming March through May. Among other insects, mosquitos are pollinators for this plant.

Site: Walker County, GA Date: 2012-March-23	Photographer: Gerald C Williamson Nikon D7000
Butterweed grows to about 2.5 feet tall. There is a main, glabrous stems which is usually distinctly striped with pink to purple. The flower heads form on stems arising from the leaf axils.
Click on the photo for a larger image
Site: Walker County, GA Date: 2012-March-23	Photographer: Gerald C Williamson Nikon D7000
The stems of Butterweed are hollow.
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Site: Walker County, GA Date: 2012-March-23	Photographer: Gerald C Williamson Nikon D7000
The leaves are pinnately lobed or perhaps lyre-shaped. There may be up to 5 pairs of lateral lobes and a terminal lobe, with the lobes getting larger toward the end of the leaf.
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References used for identification and information:

Video of Asian Tiger Mosquito pollinator:

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Packera glabella initially published on USWildflowers.com 2012-04-06; Updated 2015-06-24

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All content except USDA Plants Database map Copyright Gerald C. Williamson 2024
Photographs Copyright owned by the named photographer

Code Update 20230302