Polemonium foliosissimum

Polemonium foliosissimum, the towering Jacob's-ladder, is a rare species of flowering plant in the phlox family Polemoniaceae, native to the western United States; Arizona, Colorado, Idaho, Nevada, New Mexico, Utah and Wyoming. As its synonym Polemonium archibaldiae it has gained the Royal Horticultural Society's Award of Garden Merit.

Subtaxa
The following varieties are accepted:
 * Polemonium foliosissimum var. alpinum Brand - Idaho, Nevada, Utah, Wyoming
 * Polemonium foliosissimum var. foliosissimum - Arizona, Colorado, New Mexico, Utah