The closest this gets to a willow is the second part of its scientific name. It is Baccharis salicifolia and is part of the composite or daisy family, Asteraceae. They are large shrubs rather than trees. Calflora link below.

Here is a link that might be useful: Baccharis salicifolia

Reminds me of a Pluchea.

Very different from Baccharis halimifolia with which I am acquainted with on the East Coast. At least I got the right family.

Out here there's an upland species, Baccharis pilularis (coyote brush), Wildflowergma, that looks similar to your B. halimifolia. However, Baccharis salicifolia (mule fat) is usually found in wetlands. (I was on a marsh restoration job once where the person in charge of getting materials ordered the upland species by mistake THREE times...sigh). B. salicifolia does look very different from both, except for similarities in flowers and being dioecious.

A male plant, going by the large pistils.

Thank you everyone for helping solve this puzzle. There is no doubt that Catspa is correct; it is Baccharis salicifolia for sure. Mulefat, seepwillow. The cuttings came from the edge of the Santa Ana river in Costa Mesa, CA--about a mile in from the ocean. I am so glad to know its growing habits--they are perfect for the spot it is in. We built a water feature to attract birds and wildlife that is very successful and this plant is part of it.