Differences in leaf characteristics

Leaves of the dominant shrubs and subshrubs of CSS are soft and flexible. Leaves of the dominant shrubs of chaparral are sclerophyllous.

Leaves of dominant species of CSS and chaparral.
Leaves of dominant species of CSS and chaparral.

The flimsier leaves of shrubs in CSS are not built to last. Typically, these shrubs shed a lot of their leaf area during the summer drought. (They are drought-deciduous.) Many are facultatively drought-deciduous, meaning that they will retain their leaves through the summer drought if they receive water.

Drought-deciduous CSS
A stand of CSS dropping leaves as it goes into summer drought.

Coastal sage scrub dominants are usually not completely leafless during the summer. They often retain smaller, narrower leaves. An example from the bush monkey flower (Diplacus aurantiacus) is shown below. Leaves produced earlier in the spring are broad; they are dropped as the summer drought develops. Leaves produced later in the spring (under flowers near the tip of the stem) are much smaller, narrower, and their edges are cupped under.

Spring leaves and summer leaves of Diplacus aurantiacus
Spring leaves and summer leaves of Diplacus aurantiacus

The sclerophyllous leaves of chaparral dominants, in contrast, are tough and last much longer. These shrubs are evergreen, maintaining their leaves throughout the year.