Eryngium amethystinum

blue sea holly

Outstanding Qualities

This herbaceous perennial is grown for its architectural qualities. The spiny, leathery foliage combined with the spiky, blue-to-amethyst flowers and their surrounding silvery bracts creates real drama in a border. Eryngium amethystinum looks great in combination with some of the smaller ornamental grasses, the pairing creating a strong textural contrast. Moor grasses (Molinia caerulea) and blue oat grass (Helictotrichon sempervirens) are good possibilities. At the end of the season, this sea holly stands up well in the face of cooler, wetter weather, and creates winter interest in the border. Its seed heads also feed wild birds. This species of Eryngium is easier to grow than some of the others. Use it at the edge of a border, for structure, as a vertical accent or as a focal point.

Colors & Combos

Great Color Contrasts: gold, dark green, black

Great Color Partners: blue, silver, purple

Culture Notes

This sea holly grows best in well-drained and sandy soil with full sun. Once established it is very drought tolerant. This tough perennial is relatively long lived and resents being disturbed and is difficult to transplant due to its long tap root. Make sure it does not get crowded by its neighbors. Remove the flower stems when they are no long attractive and cut back the foliage once it has yellowed in fall.


Quick Facts

Plant Type: perennial

Foliage Type: semi-evergreen

Plant Height: 2 ft. 4 in. (0.70 m.)

Plant Width/Spread: 2 ft. 4 in. (0.70 m.)

Hardiness: USDA Zones 3 to 8

Flower Color: lavender

Sun/Light Exposure: full sun

Water Requirements: drought tolerant when established