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Thursday, October 5, 2017

Plant of the Month (October) : Shrubby Butterweed (Bush Senecio) – Senecio flaccidus var. douglasii

Very young Shrubby butterweed (Senecio flaccidus var. douglasii)
Mother Nature's Garden of Health


It’s early fall and - fortunately for the pollinators - some of the fall-blooming sunflowers are still in full glory.  We’ve already featured several of them.  But one of the more unusual garden species, the Shrubby butterweed, can still be viewed in our Garden of Health.  The scientific name is pronounced sen-EE-see-oh  FLASS-i-dus  DUG-las-ee-eye.  This plant goes by many common names including Douglas’ groundsel, Threadleaf senecio, Threadleaf groundsel, Creek groundsel, Threadleaf ragwort, Douglas’ ragwort, Douglas' shrubby ragwort and Bush senecio.

The Senecios, commonly called Ragworts or Groundsels are a mixed bag of plants in the Sunflower family (Asteraceae).  The genus Senecio is currently under revision, based on increasing DNA evidence.  It currently contains over a thousand species worldwide. Some are succulent; others are drought tolerant, but not succulent.  Some produce chemicals that are toxic and/or medicinal.  And all have yellow ‘sunflower’ type flowers.

In California, there are currently 19 native Senecio species, as well as a number of non-native, invasive species. [1]  Of the natives, the vast majority grow in the Sierra Nevada Range.  But six species are native to Los Angeles County, with three native to western Los Angeles County.  Of the local species, California butterweed (Senecio californica), Island senecio (S. lyonii) and especially Senecio flaccidus are the most common.

In fact, Senecio flaccidus has an interestingly wide geographic range.  The species is native to Southwestern U.S. and Northwestern Mexico, including Baja California.  It currently has three named varieties.  Senecio flaccidus var. flaccidus is native to the Southwest, including the Four Corners states, TX, OK and KS.  Variety monoensis is native to the drier mountains and desert washes of Southern and Central California, including the north side of the San Gabriels.  And Senecio flaccidus var. douglasii (sometimes still known as Senecio douglasii), which is widespread from the Northern California coast and western Sierra foothills to the Los Angeles basin and foothills.  The southern extent of its range is Northern Baja CA, Mexico.

In S. California, Senecio flaccidus var. douglasii usually grows along creeks and in seasonal stream beds in Foothill Woodland, Coastal Sage Scrub, Chaparral, Valley Grassland, Creosote Bush Scrub and Pinyon-Juniper Woodland plant communities. The soil is well-drained and often rocky.  Plants often get some summer moisture in the wilds.

Senecio flaccidus var. douglasii: young plants
Shrubby butterweed is a short-lived (4-6 years) part-woody sub-shrub that loses its leaves after blooming (or when drought stressed).   It rarely grows to more than about 2-4 ft. (less than 1.5 m.) tall and wide.  It creates additional branches each year, ultimately, becoming a mounded, rather open, shrub.  Our plants, raised from seed, are young and have only a few branches (photo above).  For a better idea of mature plants, see references 2 and 3, below. 

Senecio flaccidus var. douglasii: foliage
Senecio flaccidus var. douglasii has blue-green to medium green foliage.  The color becomes almost gray in full sun in hot locations.  The branches are slender and wand-like. The leaves are deeply divided into narrow, linear lobes, so the foliage is very open, giving plants a lacey appearance.  This is the most open of the native bush sunflowers we grow.  The foliage has little to no aroma.   Ranchers dislike this plant because the foliage is toxic, particularly for cows and horses.   The foliage and seeds are also toxic for humans and pets if eaten – a consideration for planting this species.

Senecio flaccidus var. douglasii: flowers at different stages
Shrubby butterweed is a summer/fall bloomer.  It can bloom off and on, with available water, from June through October (or even all year long).  We tend to think of it as a September-October bloomer in our gardens.  The flowers are a bright golden yellow, arranged in typical sunflower heads.  Both the ray and the disk flowers are yellow in this species.  Like many Senecios, the number of ray flowers is relatively few (8-14) and there is usually space between them (see below).  The flowers are showy and cheery – a welcome sight among the oranges and browns of the fall buckwheats.

Senecio flaccidus var. douglasii: close-up of flowers


The flowers attract a wide range of insects including butterflies, native bees and other pollinators. We’ve also seen Praying mantis and other carnivorous insects on this plant.  The seeds are small and dry, with a fluffy tail.  Seed eating birds, most notably the finches, eat them in the fall. 

[seeds: picture coming soon]

Senecio flaccidus var. douglasii grows in full sun or afternoon shade.  It commonly grows in well-drained soils (sandy or rocky) but ours is doing fine in clay.  This is a very drought tolerant plant, but we like to give it occasional water, particularly in August and early September, mimicking the summer monsoons.  We suspect it would do fine with more water than we give it – and likely flower over a longer season.  This plant is tough, but it needs a little water in summer, at least in the dry areas of western L.A. County.   And it’s easy to grow from seed (see below).  Plant fresh seed in fall/early winter, keep well-watered – that’s all there is to it.

Senecio flaccidus var. douglasii: seedlings
This species was occasionally used as a medicinal plant.  It is most safely used externally, as a poultice for achy muscles or for pimples, boils and skin infections.  Do not take this plant internally, and use externally only occasionally.  All parts of the plant can be toxic to the liver, particularly with prolonged use.  For more on the medical precautions associated with this plant see references 4 and 5, below.

Shrubby butterweed is little used in conventional gardens, even the water-wise ones.  The toxicity of the foliage is an issue; and there are alternative, more benign native sunflowers available.  But the Senecios have a certain look – somewhat like a golden Coreopsis – that is just what’s needed in some fall gardens.  The flowers make great cut flowers and can also be used to make a yellow dye (wash hands after handling).   In short, we like this native Senecio.




For plant information sheets on other native plants see: http://nativeplantscsudh.blogspot.com/p/gallery-of-native-plants_17.html

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  1. http://www.calflora.org/cgi-bin/specieslist.cgi?where-genus=Senecio
  2. http://calphotos.berkeley.edu/cgi-bin/img_query?rel-taxon=begins+with&where-taxon=Senecio+flaccidus+var.+douglasii
  3. http://www.smmflowers.org/bloom/species/Senecio_flaccidus_douglasii.htm
  4. http://www.eldoradowindyfarm.com/SFBG-ethnogroundselthreadleaf.html
  5. https://www.researchgate.net/publication/278051432_Pyrrolizidine_alkaloids_in_medicinal_plants_from_North_America




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