Beautiful plant, but be very careful. It can be extremely difficult to remove from unwanted areas. A raised border planter won't necessarily be sufficient to contain spread--it can send rhizomes down and then laterally. (Picture down a raised planter and under a 3-4' concrete walkway.) If brave enough, I would put it in a solid bottomed planter with just drainage holes below, on top of solid concrete. And then be very careful with the pruning pieces. Definitely do not reuse the soil. I love the look of the plant, but don't dare introduce it into my CA garden.

YES! I googled Ranuculus Sceleratus and found this plant! Thanks very much for sharing your knowledge of plants with me!!!

It is very reminiscent of a spindly Sonchus oleraceous. If you tear a leaf does it ooze milky sap? https://maltawildplants.com/ASTR/Sonchus_oleraceus.php

Thank you both. Definitely Zizia Aurea/Golden Alexanders