Allium Nigrum and a very wide selection of allium bulbs in the UK, try Bloms. Cool colors in a hot garden: allium Nigrum is planted with veronica 'Kapitan', stachys byzantia, and a cristophii.
Euphorbia ‘Blue Haze’, dark sedum ‘Ruby Glow’, nepeta, common chive, and Lamb’s Ears. Ordinary plants put together by an artist.
Papaver Juliane Poppy - Beth Chatto's 5 Favorite Flowers for a Gravel Garden