The species name "reniformis" indicates the kidney shape of roundleaf mudplantain leaves which are rounded and deeply cleft at the base. The bluish to lavender color of roundleaf mudplantain should NOT be used to separate it from ducksalad; the arrangement of flower on a stalk is more diagnostic.

In the juvenile stages roundleaf mudplantain and ducksalad can be difficult to separate, but more mature plants exhibit the rounder leaves of mudplantain in contrast to the more linear shape of ducksalad leaves. The flowers of roundleaf mudplantain are arranged on a stalk in a form called a raceme. They more closely resemble the inflorescence of water hyacinth than those of ducksalad.