That species isn't hardy (although it might have survived last winter, which was the mildest in 20 years). Caesalpinia gilliesii is generally zn 7 hardy in a well-drained, sunny spot, but tends to be short-lived wherever it is grown, even in mild climates like California. Expect it to last 5-7 years at most. It is probably easy to start from seeds although I have not tried it myself.
You could try C. pulcherrima in a pot but that may not give satisfying results.