''Polemonium caeruleum'', known as Jacob's-ladder
or Greek valerian, is a hardy
perennial flowering plant. The plant produces cup-shaped, blue or white flowers. It is native to
temperate regions of
Europe.
Growth
The plant usually reaches tall and broad, but some occasionally grow taller than . It can grow in North American
hardiness zone
A hardiness zone is a geographic area defined as having a certain average annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most wide ...
2.
Habitat
The plant is native to damp grasslands, woodlands, meadows and rocky areas in temperate areas of Europe and Asia.
Cultivation
The plant normally prefers soil that is rich in moisture and lime with partial shade. Normally hardy, some
cultivars (e.g. 'Blue Pearl') behave as tender
biennials
A biennial plant is a flowering plant that, generally in a temperate climate, takes two years to complete its biological life cycle.
Life cycle
In its first year, the biennal plant undergoes primary growth, during which its vegetative structures ...
, which means they are effectively annuals in cooler climates (below
hardiness zone
A hardiness zone is a geographic area defined as having a certain average annual minimum temperature, a factor relevant to the survival of many plants. In some systems other statistics are included in the calculations. The original and most wide ...
6).
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.
Cultivars include:
* 'Album' (white flowered)
* 'Blue Pearl'
* 'Brise d'Anjou'
* 'White Pearl' (white flowered)
* 'Snow and Sapphires' (variegated foliage)
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.
References
External list
* Biggs, Matthew, ''Vegetables, Herbs & Fruit: An Illustrated Encyclopedia'', (2006) p324-325. Firefly Books Ltd.,
* Bremness, Lesley, ''Herbs (Smithsonian Handbooks)'', (1994–2002) p205. Dorling Kindersley, Inc.,
* Howes, F.N., ''Plants and Beekeeping'', (1979) p161 Faber Paperbacks,
{{Taxonbar, from=Q162779
caeruleum
Garden plants
Medicinal plants
Plants described in 1753
Taxa named by Carl Linnaeus