Eryngium planum. This drought tolerant perennial thrives in sandy, well drained soil. Its stiff, spiny leaves are bluish green with silvery veins. It forms a clump over time, and blooms from June to September. The blue and white flower clusters each have a distinctive bract. Direct sow the seeds in autumn, or stratify in the fridge for three weeks if sowing in the spring. This involves planting into moist soil and enclosing the container in a plastic bag in the fridge. When the three weeks are up, move the bagged container into a warm room and await germination. Either way, this simulation of winter improves germination in Sea Holly seeds. This species type grows to 50cm (20") tall.