California Lilac or Ceanothus.

Ceanothus crassifolius - This plant is found in Southern California's coastal mountain ranges. It is an erect, spreading shrub which can grow to ten feet in height. The branches become long and the younger twigs are fuzzy with white or light brown hairs. The small evergreen leaves have undersides coated with hairs, thus the Hoary. The inflorescences are borne on short stalks and are small and rounded with tiny white flowers.

Photo taken at Rancho Santa Ana Botanic Garden - Claremont, CA