Until I started this post, I had no idea that Hens and Chicks are native to southern Europe. That still doesn't explain their hardiness. Neither the ferocity of a Canadian winter nor the hot, often dry, southwestern Ontario summers seems to bother these weird plants.
Succulents providing a ground cover of clusters of rosettes, I grow these plants mainly for their foliage. The largest rosettes are the 'hens', and the smaller ones springing from them are the 'chicks.' But these birds do produce flowers which sit on the top of tall, erect stalks that tower up to a foot over the foliage.
Each time our hens and chicks flower I think, "Weird."