Many of San Diego's soils are classified as heavy soils, meaning they tend to be on the clay side and this results in a soil that stays too wet and does not allow for good aeration to plant roots. The soil at the South Bay Botanic Garden is classified as a Diablo clay, and makes the growing of some plants almost impossible.
Hence, the "Dry Feet" Garden. In this small area are plants that typically grow in sandy or rocky soils, or grow on the sides of slopes. You will see some ceanothus, grevilleas, proteas, and other plants from the more arid parts of the world. The area is irrigated with a drip system and the plants are all growing in decomposed granite.