I took this photo last September while I was photographing the milkweed-fauna episodes... but it was still blooming in places along University Road as recently as last week (December). Hayfield Tarweed (Hemizonia congesta) is a rather thin-stemmed annual plant that is native to California and Oregon where it is a common component of open fields and grasslands. Like other tarweeds the stem and foliage are glandular. When walked through or otherwise crushed it has a very strong tar-like odor.
The inflorescences are covered with glandular hairs. Being in the family Asteraceae, the flowers are daisy-like, and each head has a center of whitish-to-yellowish dark-tipped disc florets.
There are many subspecies which vary in appearance. In this photo, most of the flowers appear to be sessile (attached directly by the base), so it is likely either H. congesta ssp. clevelandii or H.congesta ssp. calyculata (which is the rare Mendocino tarplant). A close look at the subtending bracts would determine which subspecies it is.
