Unusually high and late spring rainfall, a relatively large-scale disturbance (see White 1979), is associated with colonization of grasslands by the evergreen shrub, Baccharis pilularis, in northern California (Williams and Hobbs 1989) and could be necessary for coastal sage shrub seedling survival over the dry summer.
Although late spring moisture is essential for survival of evergreen Baccharis pilularis seedlings in grasslands (Williams and Hobbs 1989), coastal sage dominants respond facultatively to increasing dryness and, therefore, may not require unusually high, late spring moisture to survive through the summer drought.
arboreus, Ulex europaeus (another N-fixer), and Baccharis pilularis
frequently colonize formerly heavily grazed pasture (McBride and Heady 1968, Heady et al.
The cessation of grazing (Salvation Army and Scotts Valley High School lands, 1970's; Glenwood Open Space Preserve, 1980; Polo Ranch, early 1990's) and fire suppression have likely contributed to the increasing presence of invasive plant species (and also rank natives such as Baccharis pilularis
[coyote brush]) and accumulation of thatch.
Greene (Asteraceae); coyote bush, Baccharis pilularis
fills most of the garden; Eriogonum umbellatum grows around an olive tree's drip line.
Coyote brush, Baccharis Pilularis
``Twin Peaks,'' requires even less water than that.