Native purple owl’s clover makes showy wildflower display in Sonoma County

Blooming March and April in pink, clover-like shaggy masses on hillsides and valleys, is the annual wildflower, purple owl’s clover (Castilleja exserta, formerly Orthocarpus pupurascens).

The upright, rounded flower heads are composed of sparse, sac-like white or yellow flowers with small dark eyes, overhung with a small hooked beak, and numerous purple/pink feathery bracts. Preferring open areas, the plants are from 4 to 16 feet tall and often grow on infertile grassland found in chaparral, coastal sage or valley plant communities. The plant is a hemiparasite, and as such has a poorly developed root system. Though it does photosynthesize, the purple owl’s clover derives some nutrients such as water and minerals from other plants like grasses by “tapping” into their roots with a structure called a haustoria. The thread-like leaves are reduced in size for this reason. It is in the Orobanchaceae (Broomrape) family, which includes the Indian paintbrushes that it resembles.

The purple owl’s clover is the larval host plant for the Bay checkerspot butterfly, a threatened species.

Also common at this time of year is the field owl’s clover, Orthocarpus campestris. The numerous flowers are bright yellow and the bracts are green. The yellow owl’s clover can grow in dense, extensive masses on moist valley sites, including along roads and highways where it forms spectacular displays that can be so bright it can appear a piece of the sun has crashed to earth. Highway 101 from Santa Rosa to Geyserville is decorated with its cheerful blooms.

You can reach columnist Kate Frey at katebfrey@gmail.com. On Twitter ?@katebfrey. Or visit her at ?freygardens.com.