Answer: Jacob's Ladder is used to refer to several plants (all Polemonium). Polemonium in general grow best in partial shade to shade and like a cool moist location. Most of them have blue flowers. According to "Perennials for American Gardens" by Ruth Rogers Clausen and Nicolas H. Ekstrom it has "alternate, odd-pinnate leaves, with leaflets arranged like the rungs of a ladder in pairs, decrerasing in size toward the separate larger terminal leaflet. Erect or nodding, the blue, white, or pink flowers are loosely clustered; their campanulate or wheel-shaped corollas are 5 lobed.... Divide carefully in spring, avoid damaging the brittle stems." In my experience, they are lovely spring flowers in the woods and in the garden.
Two you might see in gardens are P.caeruleum (often referred to as Jacob's Ladder) which is native to Europe and Asia and is upright to 3'; and P.reptans (often referred to as Jacob's Ladder, Greek Valerian, or Creeping Polemonium) which is native from New York to Kansas and Alabama and is shorter at only 1 to 2'.
A quick web search using the correct Latin name should come up with additional information and photos.
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