These plants are growing in the upper part of a garden retaining wall. Although they don't need much soil or water, these lucky plants have access to plenty of both through the wall's cracks. These are alpine plants, so they can also tolerate the cold of January. They would have a harder time of it above in the garden itself because the faster growing plants there would quickly shade them out. These are hardy plants that have evolved to take advantage of areas that are too difficult for other plants.