Broom Groundsel — October 2010

Broom groundsel plant

Broom groundsel flowers

Broom groundsel seeds

A large variety of yellow-flowered plants can be found on the Preserve throughout the growing season, especially composites (members of the sunflower, or daisy family; Asteraceae) and sometimes their specific identification can be challenging. In the fall one of our most obvious and vibrant yellow-flowering composites is broom groundsel, Senecio spartioides. The genus Senecio was named by Linnaeus in 1753 from the Latin word for old man, senex, because of the whitish downy hairs covering the seed heads in this genus. Senecio, with over 1,000 species worldwide, is one of the largest genera in existence, although some taxonomists have recently proposed revisions that would move many of the species out of this genus. Senecio species are commonly known as groundsels or ragworts and there are 20 species native to New Mexico. The species name spartioides means resembling the genus Spartium, a group in the legume family, Fabaceae. Other common names for broom groundsel are broom-like ragwort, many-headed groundsel, grass-leaved ragwort, and broom butterweed.

Broom groundsel is a short-lived perennial reaching two to three feet in height that typically grows in plains and shrublands, often colonizing disturbed ground. Individual plants send up many stems from a taproot creating a rounded or hemispherical-shaped plant with a somewhat open airy appearance. The stems are all about the same height and each stem may have a woody base with leaves emerging from the stem in an alternate arrangement all along the length of the stem. Leaves are bright green in color, usually smooth and narrow, and up to four inches long. Some leaves may be irregularly divided into thin segments and often the lower leaves quickly become withered.

The flowers of broom groundsel may appear from July through October and typically form a dense layer of flat-topped clusters. Because all the blossoms occur at the same level, plants in bloom do resemble the head of a broom pointing skyward. Each single flower head has relatively few ray flowers (usually 4 – 8) with long thin bright yellow petals. The gold-colored disk flowers are more numerous, but much smaller. Individual flower heads arise from a cylindrical base (technically called an involucre) that is covered by smooth, leaf-like structures called phyllaries. The number, size, shape, and surface features of these tiny structures are often used to distinguish between species in this group of plants. Each of the flowers in the head has the potential, if successfully pollinated, to develop into a seed adorned by a crown of fluffy white soft bristles that function in seed dispersal by wind (and, coincidentally can be reminiscent of an old man’s head).

Since broom groundsel is a relatively obvious and widespread plant in our Southwestern landscape, it is not surprising that this plant has proved useful to Native Americans. Navajos are known to have used a decoction of the whole plant to produce a steam bath for treating sores. They also administrated a root decoction after childbirth to facilitate delivery of the placenta. In addition, Navajos used the root bark as chewing gum. It has been reported that Zunis would pulverize broom groundsel roots to prepare a treatment for aching bones and they would make an infusion of the flowers for application on inflamed eyes. Hopi people treated sore muscles with a poultice prepared with broom groundsel flowers, whereas a poultice of ground leaves was used on pimples and skin diseases. Broom groundsel is known to be toxic to livestock, but is rarely eaten because it is not very palatable. Furthermore it tends to turn up as randomly scattered individual plants rather than in large clumps, so grazers would be unlikely to ingest it in significant amounts. As fall transforms our grasses and shrubs to tans and browns, I am ever grateful for the occasional golden bouquets and playful white fluff balls of broom groundsel that animate our October landscape.

© 2010 Jerry Melaragno

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