Voss 'Alberta Globe'. A mutation from the well known 'Conica', but more congested, slower growing and rounded in outline. Discovered by C. Streng Jr. of Boskoop, Holland, prior to 1967.
P.g. 'Conica' (syn. P.g. var. albertiana 'Conica'). Neatly conical habit eventually to 3m. or more, but growing only 6-7cm per annum. Dense, the leaves about 1cm long, light green when young, maturing bluish-green. Discovered in the wild as a mutant plant from seed, by Rehder and Jack in 1904 near Lake Laggan, Canada. Prone to red spider mite damage in warm dry summers.
P.g. 'Echiniformis'. Flattened globose to cushion-forming, eventually to 1m. wide by 50cm tall or more, but extending only by 1.5-3cm per annum. Foliage dense, the leaves 5-7mm long, yellow-green with a waxy bright glaucous coating. Arose in France prior to 1853.
P.g. 'Laurin'. A mutant from 'Conica' but potentially dwarfer. Overall habit narrower with ascending stem tips, the annual growth increment rarely more than 2.5cm Leaves dark green when mature. Discovered by R. Arnold of Holstein, West Germany about 1952; introduced commercially in 1970.