Serpentine Groundsel

When I come upon a yellow member of the Aster Family (Asteraceae) my tendency is to overlook it. They are often so difficult, for me, to separate that I do not even try. In May there were some yellow Asteraceae in the field across from the start of the Eight Dollar Mountain Natural Botanical Area Boardwalk (Josephine County OR). The unusual basal rosette reminded me of some buckwheat (Polygonaceae) basal rosettes so I had to figure out what this plant was.

Serpentine groundsel (Packera hesperia) is found only in the Siskiyou Mountains of Southwestern Oregon and Northwestern California. Because of its limited distribution in California, serpentine groundsel is listed as a rare plant in that state. This native perennial grows in serpentine-derived soils in open woodland scrub between about 1,650 and 8,000 feet.

The plant arises from a fibrous caudex (rootstock). The basal leaves and proximal cauline (stem) leaves are petioled (stalked) and ovate to spoon shaped. The cauline leaves are sessile (no stalks) and bract-like.

The serpentine groundsel inflorescence is radiate, meaning it has both ray and disk flowers. The 8 to 13 ray flowers and the 35 to 50 or more central disk flowers are yellow with the disk flowers being a darker yellow to orange. The phyllaries surrounding the flower head are green with reddish tips and are densely tomentose (having matted woolly hairs) proximally.

The fruits of serpentine groundsel are cylindrical achenes with a pappus of white, minutely barbed bristles.

Senecio hesperius was a former designation for P hesperia. Other common names include western ragwort and Siskiyou butterwort.

John George Packer (1929 – 2019), an instructor of botany at the University of Alberta and a specialist on the flora of Alberta, the Arctic and alpine regions, is honored by the genus designation. The specific epithet comes from the Greek “hespera” meaning evening. It refers to being “of the West” because the sun sets in the West in the evening.

I am glad I took a second look at this yellow Asteraceae.

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