Marin County Asters

by Doreen Smith

California no longer has any species remaining in the Latin genus “Aster.” Now in Marin, most have been put into the genus Symphyotrichum, but it remains OK to use “aster” as the common name for these plants. (The sand aster, Corethrogyne filaginifolia, and the broad-leaved aster, Eurybia radulina, are not dealt with here.)
Marin has four Symphyotrichum species. Three are perennial: Symphyotrichum chilense, Symphyotrichum lentum, and Symphyotrichum subspicatum; one is annual: Symphyotrichum subulatum var.parviflorum.
Despite its specific epithet, Pacific aster (Symphyotrichum chilense) is a native Californian, and not from Chile. Some mix-up occurred in the Herbarium when the type specimen was named and now it can’t be changed. The most common species found in many parts of the County, it blooms summer to fall. The bracts underneath the flower head are blunt-tipped. We saw some recently in grassland near Nicasio Reservoir.
Very similar to Symphyotrichum chilense and able to hybridize with it is Douglas aster (Symphyotrichum subspicatum). This species has pointed bracts below the flower head according to the Jepson Herbarium e-Flora. I have trouble separating the two. The famous botanist Randall Morgan identified some spring–flowering plants as this species on the Lunny “G” Ranch at Pt. Reyes.
Also similar, but with linear leaves and a semi-aquatic habitat is Suisun marsh aster (Symphyotrichum lentum), most recently seen here only in late summer and fall on the shores of the Chileno Valley Laguna.
The smallest species we have is slim-aster or annual saltmarsh aster (Symphyotrichum subulatum var. parviflorum). It is found on the drying margins of fresh or brackish pools in late summer and fall. Plants are fairly abundant about the Las Gallinas wastewater ponds in some years, but hard to find in others.

Photo by Vernon and Doreen Smith

Photo by Vernon Smith

Symphyotrichum chilense – (common Pacific aster)


Symphyotrichum lentum – (Suisun marsh aster)


Symphyotrichum subulatum – (annual saltmarsh aster)