Sweet flag roots spread horizontally very close to the surface of the soil, and are a known favorite snack of the muskrat. Sweet flag spreads by means of rhizomes, a subterranean stem, thickened with deposits of food reserves. These specialized plant stems produce shoots and root systems that will develop into new plants. Rhizomes enable plants to do two things, propagate vegetatively and to perennate -- survive an unfavorable season -- hidden underground, protected from adverse elements.