- Plantain is the name for plants of genus Plantago, which are chiefly an annual or perennial weed. This rosette forming plant has many broad and rounded long stalked leaves. Each leaf is almost hairless and they can grow up to 8 inches long. All of the leaves have well defined veins. Plantain is a very common weed found throughout the United States and Canada. It can be found in bare trodden areas, in waste lands, back yards, roadsides and near rail road tracks. - The flowers are borne in spikes