In botany, a rhizome is a horizontal stem of a plant that is usually foun underground, often sending out roots and shoots from its nodes. Plants with underground rhizomes include ginger, hops, and turmeric, significant for their medicinal properties, and the weeds Johnson grass, bermuda grass, and purple nut sedge. Some plants have rhizomes that grow above ground or that sit at the soil surface, including some Iris species, and ferns, whose spreading stems are rhizomes. Rhizomes may also be referred to as creeping rootstalks, or rootstocks. A stolon is similar to a rhizome, but, unlike a rhizome, which is the main stem of the plant, a stolon sprouts from an existing stem, has long internodes, and generates new shoots at the end, e.g., the strawberry plant. In general, rhizomes have short internodes; they send out roots from the bottom of the nodes and new upward-growing shoots from the top of the nodes.