Eryngium agavifolium aka Sea Holly

Eryngium agavifolium is an evergreen perennial from north-central Argentina. Its common names include agave-leaved sea holly and agave-leaved eryngo. It belongs to Apiaceae, the carrot family. This species grows in a temperate climate within its native range. It is not native to Britain or Ireland. Gardeners grow it in beds and borders for its leaves and flowers.

The plant forms a clump with a rosette of leaves. Each leaf has a sword shape and sharp teeth along its edges. Leaves reach about 1.5 feet [0.45 metres] long. The foliage stays green through the year. Its upright form reaches 3.3–4.9 feet [1–1.5 metres] tall in gardens. Allow a spread of 1.6–3.3 feet [0.5–1 metre]. The RHS gives two to five years as the time to maturity. The leaf rosette and branched flower stems give the plant distinct forms.

Small green flower heads grow on the branched stems. Each head has a shape like a thimble. The RHS places flowering in late summer. Chicago Botanic Garden lists blooms from May through August. These sources therefore give different flowering periods for the same species. The flowers add green rather than a bright contrasting colour. The plant suits flower beds, borders, and cottage-style gardens. The RHS also lists coastal, courtyard, and city gardens as planting settings.

Choose a site in full sun with soil that drains well. The RHS recommends dry soil with low to moderate fertility. It lists both loam and sand as suitable soil types. Acid, neutral, and alkaline soils all fall within its stated range. The plant resists drought, and Chicago also lists dry growing conditions. Protect it from wet soil during winter. The RHS rates it H4 for UK conditions. Chicago lists USDA hardiness zones 5–9. These ratings come from different systems and should remain distinct.

Cut back the plant once flowering has finished. Raise new plants from seed or divide existing clumps. Watch for leaf and bud eelworms, slugs, and snails. Root rot and powdery mildew may also affect it. Good drainage remains a key part of the stated growing advice. The supplied sources give no details about fruit or edible parts. They also provide no evidence about human or pet toxicity.