''Polemonium caeruleum'', known as Jacob's-ladder
or Greek valerian, is a hardy
perennial
A perennial plant or simply perennial is a plant that lives more than two years. The term ('' per-'' + '' -ennial'', "through the years") is often used to differentiate a plant from shorter-lived annuals and biennials. The term is also wid ...
flowering plant. The plant produces cup-shaped, blue or white flowers. It is native to
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (23.5° to 66.5° N/S of Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ranges throughout ...
regions of
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
.
Growth
The plant usually reaches tall and broad, but some occasionally grow taller than . It can grow in North American
hardiness zone 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
cultivar
A cultivar is a type of cultivated plant that people have selected for desired traits and when propagated retain those traits. Methods used to propagate cultivars include: division, root and stem cuttings, offsets, grafting, tissue culture ...
s (e.g. 'Blue Pearl') behave as tender
biennials, which means they are effectively annuals in cooler climates (below
hardiness zone 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
A leaf spot is a limited, discoloured, diseased area of a leaf that is caused by fungal, bacterial or viral plant diseases, or by injuries from nematodes, insects, environmental factors, toxicity or herbicides. These discoloured spots or lesions ...
and
powdery mildew
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of ascomycete fungi in the order Erysiphales. Powdery mildew is one of the easier plant diseases to identify, a ...
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