Rhizomes are not roots. They are stems that grow horizontally. These stems usually grow beneath the ground. Iris, as well as asparagus, ginger, and hops, have rhizomes. Rhizomes have two purposes. The first is that they make the new roots and push them down into the soil. Secondly, rhizomes can grow new stems and pushes them out of the earth. Rhizomes can store proteins and starches, or those materials that allow the plant to survive a bad season.