It's well past peak bloom. Roughly one foot tall, reliably perennial, sets lots of seed. Very rare in nature (the Pacific coast near San Francisco), but quite easy in the garden (at least here).
Very nice and interesting, Gene. Is it reasonably slug resistant? And do you have some seeds to spare, please?
I've always been fascinated and desirous of the western North American delphiniums, particularly those that break the genus predominance for blue flowers, so species like D. luteum and D. cardinale hold particular interest for me. Years ago, a couple attempts at raised these species from seed did not succeed. And to address Trond's question about these plants attraction to slugs, see the Pacific Bulb Society link below, apparently these are indeed slug magnets.
D. luteum is listed as Fedarally Endangered, so I suppose that means seed is not supposed to be distributed? Although, the Statre of California just lists it as "rare", so I'm not sure which status prevails.
Some pertinent links for this delightful little Delphinium:
It is listed by the State of California as Rare and by the Federal Government as Endangered.
The Pacific Bulb Society has a nice gallery of western North American delphiniums, including D. luteum, the red D. cardinale, and various hybrids.