Agave Attenuata
The ultimate architectural plant that is perfect in pots as well as in the garden. The dramatic structural foliage is almost completely neglect-proof and thrives in a wide variety of climates and locations.
Protect from frost. Divide clumps when over-crowded or remove pups regularly with a sharp knife and pot on for use in other areas of the garden. Plant will die after flowering, but this does take a long time (10+ years) and there are always new pups ready to take this older plants place.