This grower is sure of this plant identification.
Gray-green narrow fleshy leaves with white margins and a cotton like fringe. Will take some frost if dry in winter.
Agave filifera (Thread agave). This is a compact perennial succulent. The leaves are produced in rosettes of lance-shaped dark green leaves which are about 25cm long and edged with white fibres. The flowers are spikes with dense clusters of green-white blooms borne on erect stems up to 2.5 metres high in late summer and early autumn.
If you grow them under glass, grow them in a standard compost with full light. When grown outdoors the soil should be moderately fertile, a little acidic and sharply drained with full sun.
Grown for their form and foliage.