Sempervivum Extra (July) Sempervivum Extra (April) Extra Large, flat rosettes, brown tips of pale green leaves. £2.75 Out of stock. A stunning variety, it really does offer something extra. Fairly large rosettes, perfectly symmetrical, pale green in the centre with eye-catching reddish-brown tips. It's a beauty. A natural form of Sempervivum calcareum but given the cultivar name 'Extra' by Howard J. Wills.