|Ceanothys thyrsiflorus, aka California lilac. Native to California and Oregon, common here.|
The lilacs have bloomed and faded. Now, the blue blossom takes over and will bloom through June. The blue is more intense, the tree denser than the lilacs. But they don't perfume the neighbourhood like a lilac does.
A few other tidbits of information about Ceanothus thyrsiflorus: the blue flowers can be used to make a green dye (though why green rather than blue?), and all parts of the plant can be crushed and worked into a lather to use as a gentle soap, as the plant contains saponins. (From UBC Botanical Garden)
And butterflies and bees love it, too!