Eryngium planum

Eryngium planum is a lovely species from Eastern Europe with heart-shaped leaves and steel-blue flowers in summer. This attractive sea holly forms clumps of evergreen, soft, deep green heart-shaped leaves. In early summer, the thin wirey stems emerge, set with spiny leaves.
Tiny, stemless, steel-blue flowers tightly packed into egg-shaped heads resembling thistles appear in profusion in summer in well-branched clusters at the stem tops. Each flower head is subtended by a narrow, spiky collar of spiny, blue-green bracts.

The plants grow to a height of 60 to 75cm (24 to 30in) tall with a spread of 45 to 60cm (18 to 24in). They are tolerant of hot, dry sites, of poor soils and of soil high in salts and are easily grown in dry, sandy, well-drained soils in full sun. Tall plants may sprawl and need staking, particularly if grown in overly fertile soils or in anything less than full sun.
Eryngium planum is a very hardy species, they are effective as a single specimen or in groupings and provide superb colour throughout summer. The flowers are adored by florists for their unique texture and long lasting flowers which add interesting colour and texture to bouquets or the garden. Each individual floret is rich in nectar so the prickly flowers are popular with bees.

Sowing: Sow October to February or March to September
The seeds may need a period of cold to enable them to germinate.
Sea holly has very long roots that penetrate deeply in the soil and are often several feet long. The plant should be placed in its final position whilst small since it resents root disturbance.

Sowing October to February.
Sow in John Innes seed compost or something similar, cover with a thin layer of compost. After watering place the seed container in an unheated greenhouse or coldframe.
Germination is irregular, between 5 and 90 days. As each seed germinates transplant into its own pot containing gritty compost to grow on, until large and strong enough to be planted outdoors into its final position in the garden.

Sowing March to September.
During the warmer months, you can “imitate the winter” by using the following method of stratification:
Sow in John Innes seed compost or something similar, place each container in a polythene bag and put into the refrigerator (not the freezer compartment) for 2 to 3 weeks. (Fridges are the deal temperature at around 4°C (39°F)
After this time place the containers outside in a cold frame or plunge them up to the rims in a shady part of the garden border and cover with glass or clear plastic. As each seed germinates transplant into its own pot containing gritty compost to grow on, until large and strong enough to be planted outdoors into its final position in the garden.

Cultivation:
Eryngiums key requirement is that gardening oxymoron - moisture-retentive soil and good drainage. This equates to rich alluvial or humus-rich soil that holds moisture without getting waterlogged in winter. The plants particularly dislike cold, wet soil in winter which may cause the crown to rot. If planting on heavy soils, dig in plenty of coarse grit to improve drainage prior to planting.
Divide mature plant in early spring or autumn, take care since the plant resents root disturbance.
Although you can cut back flower stems after flowering, the seedheads are a very attractive feature so are usually left over winter. Tidy dead and decaying foliage in early spring to discourage rot.

Plant Uses: Costal or Gravel Gardens. Cottage/Informal Gardens, Flower Arranging, Borders and Beds, Wildlife Gardens Attractive to Bees and Butterflies.
Beloved of flower arrangers for their striking foliage and flower heads.

Cut Flowers:
To use the blooms for dried flower arrangements, cut the flowers before they are fully open. Simply cut with a knife or secateurs. The difficulty is deciding when the stem is ready for cutting. In general, the flowers on the stem should be turning an appropriate blue colour. This process can take up to 10 days from the time it is first noticed. Avoid the temptation to cut back all the flower-heads in autumn as they provide interest in the winter garden.

Origin:
Eryngium is a genus in the family Apiaceae of about 230 species of annuals and perennials with hairless and usually spiny leaves, and dome-shaped umbels of flowers resembling those of thistles.
The genus has a cosmopolitan distribution, with the centre of diversity in South America. Some species are native to rocky and coastal areas, but the majority are grassland plants, their prickly leaves are a defence to deter grazing animals.
Eryngium planum is native to central and southeastern Europe and central Asia.

Nomenclature:
Eryngium is derived from the Greek word hruggion, a name given by Theophrastus for 'a spiny leaved plant'.
The species name refers to the plain leaves.
Common names of the genus include Sea-holly and Eryngo, the former typically being applied to coastal species, and the latter to grassland species.
Eryngium alpinum is commonly known as the Alpine Sea Holly. Despite its name and appearance, this is unrelated to the more familiar holly and is in fact an umbellifer: one of that large and confusing family which includes the parsleys, carrots and parsnips.