I live within 300 yards of ocean in northern California. My two plants, about 6 inches tall, resemble a holly with deep green leaves with numerous prickly points on edge. How high and what shape will it take? Does it need a lot of sun or will underneath ashore pine be ok?
Hopefully this article will answer your questions: http://ucanr.edu/sites/scmg/Plant_of_the_Month/Baccharis_pilularis/