This is a white-bracted cultivar of Crown-of-Thorns Spurge (Euphorbia x lomi cv.). This is a hybrid cross of E. lophogona and E. milii. Both parent species are native to Madagascar and also grown for ornament. Euphorbia x lomi cultivars have been bred for large bracts in a range of hues including white, yellow, pink, orange, and red. Though somewhat tender, these plants survive light frosts to the high 20ºs F in my garden, especially when kept dry under a porch roof or overhang.