Common mare’s-tail looks like a robust green bottlebrush growing in patches primarily in the shallow areas of streams, ponds, and lakes or on wet muddy shores when water levels drop. This plant is characterized by unbranched stems, abundant whorled leaves, and inconspicuous flowers. The leaves and stems vary in form depending on whether they are growing underwater or are emergent. The underwater plant portions are limp, flexible, and have very long leaves. Emergent portions are stiff and erect, with short narrow leaves.