Ornamental onions can be great garden plants as well as long lasting cut flowers or dried seed heads and if you get too many you can eat the surplus! This species that flowers in high summer on 50cm. tall often twisted stems is a favourite of mine for all the above reasons and it makes goodly clumps fast and will even self seed gratifyingly. As it is a fine delecate looking thing (not by constitution) it won’t swamp its bed fellows so is too many ever enough!
It is commonly called Keeled Garlic due to the long persistent bracts that inclose the flower buds and in bloom to looks like a mauve fireworks display. Any open sunny aspect with well drained soil will do especially if it has a little low growing ground cover of some sort to help disguise its foliage which dies off as the flowers come out like so many Onions do. I have plants in 3″ tubes at $6.50