View photos of the medicinal plant Ceanothus leucodermis (Chaparral whitethorn), profiled in Medicinal Plants of the Western Mountain States (as Ceanothus spp.).

A passage from Medicinal Plants of the Western Mountain States:

I believe most, if not all, western Ceanothus species can be used like Ceanothus americanus, just as long as the root or root bark is non–woody and reddish–tannin pigmented. My personal favorites, due to their flexible reddish roots, are the young shrubs of ‘Group C’, often called Lilac bush (blue flowers), but if those types are not in your local area: unearth, investigate, and utilize what’s nearby.