Agave filifera

From Central America, known as the Thread Agave due to the white threads that can be seen amongst the margins of the narrow spiney leaves.  Grows relatively rapidly and enjoys a sunny well drained spot.  Borderline hardy in the right position when a good size, but is a bit of a gamble unless in a mild part of the UK.  When mature can produce a flower spike up to 2m tall – quite a talking point!