Stay out of the poison oak in Southern California.  I have learned 2
thing:  (1) Poison oak is the 2nd most common plant in Southern
California.  (2) You can get the oils on you from the bushes even though
the bushes have dropped all their leaves.  Without leaves, they're very
difficult to notice/identify.

Think about it... caches are usually hid in brush a little ways off of
normal trails.