Like many of the pondweeds, P. amplifolius has two types of leaves, a submerged form and a floating form. In this case, the submerged leaf is markedly different in color and shape. The submerged leaf is folded and curved and often brownish in color (taco-shaped), while the floating leaf is green and somewhat rounded and oblong in shape.

Potamogeton crispus - Curly-leaved Pondweed (INVASIVE)

P. crispus can be identified by its distinctive leaves. The leaves are stiff, have wavy edges, and a prominant toothed margin. The leaves also have distinctive veination, with a strong center vein with opposite side veins. The leaf margin is separated from the main leave by a thin vein that runs near the outside edge of the leaf. Leaves are usually close together with some branching near the ends, with a color from light green through brownish-red. Stems are slightly flattened.

Potamogeton diversifolius - Variable-leaved Pondweed

Potamogeton epihydrus - Leafy Pondweed

P. natans has larger, oblong floating leaves than many similar-looking pondweeds

P. oakesianus is similar to P. natans

As with many of the pondweeds, the fruiting structures of P. oblongus are important for identifying to species. There is little differentiation between submerged and floating leaves, however.

Common in lakes and ponds. Look for leaf bases that clasp stem and lack of stipule (appendage at base of leaf). Lower leaves tend to be somewhat larger than upper leaves. Can be mistaken for Eurasian watermilfoil (Myriophyllum spicatum) when seen from a distance due to similar growth habits (see last pictures in this section).