How Flowers Grow
Flowers need certain things to grow. For most plants, they require soil to protect the roots from the damaging effects of the sun and to provide nutrients. Plants also need soil to provide an anchor in which to grow. Along with soil, plants need water and light. Some plants can grow without soil, and can grow in water or sand. There are also air plants that can be suspended and grown successfully. Most plants cannot grow without soil.
Where Does Soil Come From
Soil is not just dirt. Soil is made from decaying organic material and the breaking down of rocks. The decomposition of the animals to make the soil is referred to as biodegrading. Biodegrading releases nutrients and small particles into the soil that are excellent for the growth of plants. Erosion of rocks forms the hard portion in soil that gives the soil stability to act as an anchor. These small particles find gaps and holes to settle in. They are carried by the wind, along with flower seeds. When the seeds, by chance find the cracks and crevices, the result is flowers that appear to be growing out of the rock.
Growing in the Rocks
Most flowers require many more nutrients than can be found in cracks and crevices, so the majority of flowers cannot survive on rocks. This is why you do not often see flowers growing there. Moss and lichen are not traditional flowering plants and do not have the same root systems that traditional plants do. They require wet conditions to grow. Moss can grow nearly anywhere, and will attach itself to the tiny amounts of soil on rocks.
Rock gardens, also called rockeries, are gardens where large amounts of rocks are piled up on top of one another or used as landscape decoration in a designated area. This creates natural gaps where flowers and plants are rooted and can give the appearance of flowers growing in the rocks. In reality, they are using the small amounts of soil underneath the rocks. Flowers and trees can be rooted next to the sides of rocks but are growing above them which can give the appearance of the plants growing out of the rocks.