Eryngium

This has to be the spikiest plant in the garden, by far, and the spines are very hard, so falling into it would be a seriously bad idea. But it does look great as an architectural element in the border, and when it flowers will be pricklier still. The flower heads and surrounding parts (sepals?, leaves?, I'm not sure) are still green, but will turn to metallic blue as the flowers open. It always seems to be a completely unlikely colour for a plant, but there it is. The bees adore it and will be glad of something to move on to as the alliums finish. Eventually it all goes brown and will stand the winter until it gets chopped back ready for next season.