Allium caeruleum's true blue flower balls might not be as big or as perfectly spherical as more well-bred alliums, but perched on long naked stems, when spring foliage has all but gone, they are every bit as architectural. 

Flowers are just 4cm (1.5") across, among the smallest of the round alliums on stems to 45cm (18"). 

Hailing from the dry steppes of Russia and China, they prefer dry summers. 

Look for aerial bulbils on the flowers which can be planted in the same way as bulb bulbils.