A garden can live wherever a plant can grow. When we scan our surroundings for a place to begin, we look for soil. All the soil on earth is either ground up rock or decomposed plant matter. One of my favorite small ecosystems is the top surface of giant boulders. There is a cliff nearby in my town. Below the cliff face lie hundreds of car-size granite boulders wedged together in a massive jumble of caves and tilted tables. Oaks and maples have wedged themselves between the tumble of fallen rock and over time, rock-cap ferns have grown in the leaf-made humus and now carpet the upper surfaces of these giant rocks. In this one hillside, I can look up hundreds of feet to the sheer wall of rock and from there I can scan the slope to my feet on the ferns. It is the whole story of soil.
On the Aran Islands off the west coast of Ireland, all the soil has been made by the inhabitants. Over ten centuries, islanders have hauled baskets of seaweed and barrows of sand until the walled fields could support their grazing stock and their intensive vegetable gardens. Perhaps it all began with a fisherman wishing for a bit of green to go with his fish dinner.
This garden has been planted on the fireboat dock below the Oakland Bay Bridge in San Francisco.