The Jacob's-ladder (Polemonium caeruleum) belongs to Polemoniaceae (the Phlox family). It is a perennial herb that is native to the temperate regions of Europe and Asia. It grows in damp meadows, woods, and meadows, and is 45-60 cm tall. The leaves are oddly pinnate and alternate, and the leaflets are ovate to lanceolate with pointed tips. The photos show the white-flowered variety (f. album). The Chinese name is "hua ren" (花荵).