Eryngium yuccifolium

Looking a bit like a Yucca and once used by pioneers and Native Americans as an antidote to rattlesnake venom, this American tall grass prairie dweller brandishes bold bluish green lax rosettes.
Characterised by parallel veins, bristly edges and a glaucous finish, the long sword-shaped leaves launch an architectural wonder of tight set thistle-style, white spheres and pointed ivory-white bracts housed within branched clusters on smooth stiff stems.

A low maintenance perennial that provides fantastic winter interest, and unlike many species of Eryngium, more moderate levels of moisture are required by E. yuccifolium. They love well-drained soil in the open sun, and are an arresting addition to the mixed border, especially when planted amidst other sun lovers such as Rudbeckia, the Achilleas, and softer textured grasses. The eye-catching unique structure and colour make it highly desirable to gardeners as accent plants in borders and wildflower meadows.
Excellent in fresh or dried arrangements, the flowers are borne on tall branching stems, and the terminal blooms hold their colour while lateral flowers develop, until the entire stem is covered with mature blossoms.

Each individual floret is rich in nectar so the prickly flowers are popular with bees and the seeds are also loved by birds. In winter the dried seed heads look equally attractive in the garden so leave the dried seed heads on the plant over winter for continued interest.

RHS Flower Show Tatton Park 2015:
Eryngium yuccifolium was featured in The Sunset Garden designed by Tamara Bridge at RHS Flower Show Tatton Park 2015. One of three finalists to go forward to build a show garden Tamara won both a Gold Medal and The RHS Young Designer of the Year.

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.
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.

Nomenclature:
Eryngium is derived from the Greek word hruggion, a name given by Theophrastus for 'a spiny leaved plant'.
The species name yuccifolium means 'with foliage like the yucca'
Common names of the genus include Sea Holly and Eryngo, the former typically being applied to coastal species, and the latter to grassland species. 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.
This species is commonly known as the Button Sea Holly and in the US it is known as Rattlesnake Master.
This common name comes from historical use by Native Americans as a remedy for rattlesnake bites though it was more often used to brew a medicinal tea.
However erroneous this belief sounds, James Adair, an 18th century Irish historian who lived and studied Native Americans for much of his life, recorded stories of warriors applying a preparation of this plant to their arms as protection from the ill effects of venom.