So my mystery plant is no longer a mystery.
Years ago I found a scraggly one gallon shrub with interesting leaves etc at Daylily Hill Nursery in Escondido (hidden . . . get it?). The nursery worker really did not know what it was, nor did I, nor could I find anything like it on the internet and even my plant geek nephew couldn't place it. But I planted it anyway, and imagined it to be akin to the beautiful and bountiful rabbitbrush seen in New Mexico on a summer trip.
The thing has grown well in my parkway, land of little irrigation and not too much rain these past few years. It's now about 4 feet all around and covered in yellow flowers, and it even has offspring of the cloned persuasion accompanying it further on down the strip. One time Mr. Cardui and I saw one, a big one about 8 feet tall, also covered in flowers as we drove down a nearby business district avenue. The thing is, this is a plant that makes itself noticed while in bloom and then, after the flowers fade it goes unnoticed.
Well, I took another trip to Escondido, same nursery under a new name and what do you know? They had a full block of the mystery plant for sale. So say a proper hello at last to "Athanasia acerosa" also known as Coulter bush. Hales from South Africa. Not a lot of info about it out there, but here's what I've learned:
A bit hard to get started from cuttings, but worth a try. Not sure what the ultimate size is. It grows long stems from the base which flower on the ends. I've had good luck cutting these back halfway or even all the way to the base. Next year new stems sprout. Young plants are really leggy, but can be cut back in the same way to get them more bushy and full. Doesn't need much water. The flowers are sweetly fragrant and they attract a lot of small buggies.
I saw various plant bugs (seriously, miridae),
spittle bugs (Clastoptera lineatocollis), aphids (unidentified very small black ones) and evidence of their wasp parasites (over half were mummified), a ladybird beetle (Asian),
a molting sharpshooter-style leafhopper (likely Homolodisca vitripennis) and where there's prey there's the apex predator of its little golden flowery world: a mantis nymph (Stagmomantis).
So, one tiny null zone of information has been filled in, a whole tiny world of unanswered or even yet to be imagined questions.