Polemonium caeruleum, known as Jacob's-ladder or Greek valerian, 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. 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).
The plant does not have serious insect or disease problems. Leaf spot and powdery mildew can be problems, particularly in humid climates. The foliage may scorch if the plant gets too much sunlight. The leaflet tips will brown up if soils are allowed to dry out. The foliage will generally decline and become less attractive as the summer progresses. It is important to keep an eye out for slugs.
Cats are attracted to the scent of the plant, particularly younger plants.
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.
Bees work the flowers for both pollen and nectar. Flowers of other species of Polemonium are also useful honey bee forage.
The plant is known to have a few landscape uses as well such as attracting beneficial insects. The plant itself is convenient for container planting due to the shape of its growth. The flower may be presented as a cut flower or foliage and may be added to bouquets for its pleasant smell. It can be grown in a perennial border or rock garden.
- The Plant List: A Working List of All Plant Species, retrieved 11 May 2016
- "BSBI List 2007". Botanical Society of Britain and Ireland. Archived from the original (xls) on 25 January 2015. Retrieved 17 October 2014.
- "Polemonium caeruleum". Missouri Botanical Gardens. Retrieved 10 November 2016.
- "'Snow & Sapphire' Variegated Jacob's Ladder". Paghat the Ratgirl. Retrieved 11 May 2016.
- Howard, Doreen G. (2006). "From Backyard to Big Time" (PDF). The American Gardener. American Horticultural Society. 85 (6): 17. Retrieved 10 May 2016.
- "County Flowers". Plantlife. Retrieved 19 August 2013.
- "School of Horticulture Plant Database". Kwantlen Polytechnic University. Retrieved 10 November 2016.
- Biggs, Matthew, Vegetables, Herbs & Fruit: An Illustrated Encyclopedia, (2006) p324-325. Firefly Books Ltd., ISBN 1-55407-126-7
- Bremness, Lesley, Herbs (Smithsonian Handbooks), (1994–2002) p205. Dorling Kindersley, Inc., ISBN 0-7894-9391-8
- Howes, F.N., Plants and Beekeeping, (1979) p161 Faber Paperbacks, ISBN 0-571-11358-3
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