Eryngium pandanifolium aka Giant Sea Holly

Eryngium pandanifolium is an evergreen perennial in the carrot family, Apiaceae. Its native range covers southern Brazil, Paraguay, Uruguay, and northeastern Argentina. It grows mainly in subtropical regions, reaching into the tropics. It has also spread beyond gardens in southwestern Europe. In Portugal, it grows along ditch banks. Useful Tropical Plants lists it as a potential weed.

The plant forms a thick clump of long, sword-shaped leaves. Their blue-green blades have spines along the edges. Leaves can reach about 5 feet [1.5 metres] long. Garden plants reach 5–8 feet [1.5–2.5 metres] in height. Their spread reaches about 3–5 feet [1–1.5 metres]. The RHS gives two to five years to reach full size. Its bold leaf shape suits plantings that need a strong outline.

Tall flower stems rise above the leaves in late summer. Branches grow from leaf joints along the stems. They carry many small, rounded heads with a purple-grey tint. These heads can turn deep brown unless frost cuts them short. Bees, flies, and beetles pollinate the flowers. The plant is also self-fertile. Its height and form suit borders, informal gardens, and courtyard beds. The RHS also suggests it for coastal gardens. Useful Tropical Plants notes that it can grow among coarse grass.

Grow it in full sun with shelter from harsh exposure. The RHS calls for fertile soil that drains well but stays moist. It also lists the plant as drought resistant. Useful Tropical Plants says it prefers light, sandy ground. It can also cope with lime and poor gravel soils. The RHS accepts acid, neutral, and alkaline soil. Its UK hardiness rating is H4. Plants For A Future gives USDA zones 7–10. These ratings describe different climate systems rather than matching limits.

Plant young specimens in their final spot to limit root disturbance. Divided clumps may take time to settle and grow again. Sow ripe seed in containers in a cold frame. Other methods include spring division and root cuttings in late winter. Cut down spent flower stems once flowering ends. Slugs, snails, and leaf or bud eelworms may cause harm. Root rot and powdery mildew are also possible problems. The leaves yield fibre used to make cord. The sources report no known food or medicinal uses. They also list no known hazards, but this does not prove safety.