This section is from the book "Commercial Gardening Vol2", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
Although there are several species of Iberis the one most popular is I. umbellata, a pretty South European annual 6-12 in. high, having purple umbels of blossom. There are several varieties, such as atropurpurea, deep crimson; carnea, flesh; and dwarf forms also of various shades. They are all easily raised from seeds sown in gentle heat in spring, the young plants being sold in clumps or in shallow boxes for bedding out. Other annual Candytufts are I. violacea, 3 in. high, purple; J. coronaria, pure white, with some fine forms; I. Bemardiana, 6 in., pink; and the common British Candytuft (1. amara), 6-9 in., white.
Amongst the perennial kinds are I. correoefolia - a cross between sempervirens and saxatilis, 1 ft., evergreen, white; gibraltarica, 1-2 ft., evergreen, white, with pinkish shades; petroea, 3 in., white; saxatilis, 3-6 in., evergreen, white; sempervirens, 9-12 in., white, with several varieties, including a double one.