Jacob's Ladder or Greek valerian (Polemonium caeruleum) is a hardy perennial flowering plant. The plant produces cup-shaped, lavender-coloured or white flowers. It is native to temperate regions of Europe.
The plant usually reaches a height from 45 to 60 centimeters (18 to 24 inches), but some occasionally will be taller than 90 centimeters (35 inches.) The spread of the plant is also 45 to 60 centimeters. It can grow in North American hardiness zone 2.
The plant normally prefers soil that is rich in moisture and lime and does not require as much sunlight as other plants. Depending on the conditions, it will need varying amounts of water in the summer. If it is hot summer, the plant may require extra water. If it is an average summer, it probably won't need extra water. Normally hardy, some varieties (e.g. Blue Pearl) behave as tender biennials, which means they are effectively annuals in cooler climates (below hardiness zone 6).
Cultivated varieties include Blue Pearl and Brise d'Anjou. White flowered (Album, White Pearl) and a variegated (Snow and Sapphires)  variety are available.
(Cats are attracted to the scent of the plant, particularly younger plants. A person who is growing Greek valerian in a container or home garden should protect the plants if they own a cat.)
Historical medical uses
The plant was first used as a medicinal herb in ancient Greece. The ancient Greeks used the root to treat dysentery, toothaches and animal bites. The plant was also found in a few European pharmacies during the nineteenth century and was used as an antisyphilitic agent and to treat rabies. Today, the plant is not usually used medically.
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