Virginia Tech Weed Identification Guide

Variable-leaf Pondweed or Waterthread Pondweed:

Potamogeton diversifolius

pondweed7-16.jpg (58414 bytes) Weed Description:  A perennial with both floating and submersed leaves that are elliptic to oval in outline.  This weed is a common aquatic weed of ponds, streams, and lakes that is found throughout the United States.
Leaves:  Both floating and submersed leaves occur on the same plants.  Floating leaves are elliptic to oval in outline, reaching 2 inches in length and ranging from 10 to 20 mm in width.  Floating leaves usually have 7 to 11 distinct veins.  Submersed leaves are arranged alternately along the stem and are usually smaller than the floating leaves.   Submersed leaves have 3 veins, only 1 of which is usually noticeable.   Submersed leaves have stipules at the base of the leaf petiole that forms a sheath around the stem. vlpndwd7-30.jpg (30360 bytes)
vlpndwd6-18.jpg (147737 bytes) Roots: Small, thin, rhizomes and fibrous roots.

Fruit: An achene that is very small.

Flowers: Flowers are spikes that occur on short flower stalks (peduncles) and arise just above the water surface. vlpndwd7-30b.jpg (21798 bytes)
vlpndwd7-30c.jpg (24250 bytes) Identifying Characteristics:  The relatively small elliptical floating and submersed leaves and distinctively veined leaves of this plant helps to distinguish it from most other pondweeds.