- Name: White Polemonium - Other Common Names: Jacob's Ladder - Scientific Name: Polemonium Caeruleum White - Color: White - Plant Seeds: Outdoors After Frost / Indoors Weeks Before Last Frost - Bloom Time: Mid Summer - Hardiness Zone: 3 - 9 - Plant Height: 24" - Plant Spacing: 12 - 15" - Light Requirements: Sun - Part Shade - Soil & Water Preferences: Average - Quantity: 50 Seeds - Other: This Herb Gets Its Name ‘Jacob’s Ladder’ Because Its Ferny Leaves Are Arranged In A Ladder-Like Pattern Going Up The Stems Of The Plant. The Flowers Of This European Native Are Fragrant.