Dwarf Mountain Groundsel

When Leonard and I climbed Mount Lassen in August, we saw groundsel plants high on the mountain near the summit. When I tried to identify these plants I wandered into a taxonomic muddle. First I determined that this was Senecio fremontii. But there are at least four varieties. I finally decided the plants we observed high on the flanks of Mount Lassen were dwarf mountain groundsel (Senecio fremontii var occidentalis) – also commonly called Fremont’s butterweed and western Fremont’s groundsel, among other names. Just before I wrote this post I discovered a September 2019 article by Guy Nesom in “Phytoneuron” that considers S fremontii var occidentalis to not be a separate variety, but included in S fremontii. Sometimes I wish I were a better taxonomist. However, for this post I will remain true to my first impulse and continue to call this native perennial S fremontii var occidentalis. Confused?

Dwarf mountain groundsel is found in alpine rockslide areas of California and Western Nevada. The stems, often purple tinged, arise from a branching rootstock. The stems are decumbent at the base and without hairs.

The alternate, stiff, fleshy leaves are spatula-like and have blunt teeth. In this variety the distal leaves are less well developed than those closer to the base.

A member of the Sunflower Family, Asteraceae, dwarf mountain groundsel flower heads are solitary at the end of stems. The short peduncles (stalks) are hairless. Each flower head is surrounded by a single row of long, linear bracts (phyllaries). There are also a few shorter bracteoles. The radiate head is composed of 35 to 45 yellow disk flowers surrounded by a few yellow ray flowers.

The achenes (seeds) are roundish in cross section and tipped with soft, white bristles.

Senecio, the genus name, comes from the Latin “senex” meaning “old man” and refers to the grey hairs on the seed. John Charles Fremont (1830 – 1890) explored the Western United States during four journeys during which he collected botanical specimens along with his other duties and is honored by the species designation. The variety means “western” in Latin.

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