Extract from their About page:

Before the monks made this island an oasis of prayer and meditation in the sixth century the possibility of living here was practically zero: rock and limestone, little soil between one limestone slab and the next and insufficient possibilities for cultivating a field and raising livestock.

The small quantities of soil were extracted from the fissures between the stones and mixed with sand and seaweed.

Screenshot 2015-01-03 17.02.26