polemonium jacob's ladder
Polemonium caeruleum, commonly called Jacobâs ladder, is a generally erect, clump-forming perennial that typically forms a foliage mound to 18-24â tall and as wide. Odd-pinnate compound bright green leaves (to 27 leaflets each) appear ladder-like, hence the common name. Cup-shaped, deep blue flowers with contrasting yellow stamens appear in loose, drooping, terminal clusters (cymes) in spring (April-May in the St. Louis area).