What is this shrub? (Southern California)

My two-year old, two-foot tall shrub is a broadleaf (not deciduous).
All of the stems are light green and have a bumpy surface (similar to scales on a fish or shingles on a roof).
The petioles have an alternate arrangement and are spaced about every 1/2 inch along the stem.
The leaves are compound (multiple leaves arise from each petiole). They have a linear shape (the midpoint is wider than its base and its apex), have pinnate venation and have smooth margins. They are light green color with a dull surface and they feel somewhat leathery.
The white star-shaped (?) flowers are single flowers (they do not grow in spikes (racemes).
The shrub has a peppery taste even when one is just working the soil near it or pruning it.
What is it?
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