More than 60 plant families have succulents. But some of those are dominantly succulent, such as the Crassulaceae (lat. crassus = thick, fat) with thick, fleshy stems and leaves due to special water-storage tissues. They are widespread but are concentrated in arid regions of the world, particularly in Southern Africa. There are c. 40 genera but only four are native in Portugal. In our territory they grow on sands, maritime dunes, rocks, walls, rooves, cliffs, all habitats where water runs out quickly and is available for short periods.
These plants have a modified form of CO2 fixation and photosynthesis that has been named after the family — Crassulacean Acid Metabolism (CAM). Unlike most plants, the stomata of many of these plants are closed during the day and open at night. As a result, the loss of water (transpiration) during the hot dry daytime hours is minimized and carbon dioxide uptake occurs in the dark and the coolness of the night.
Many of these species became well-known as ornaments as their cultivation is easy.