Pondweed is a plant that grows in water, especially calm water. Pondweeds have small, green flowers that stand above the water. They often have two kinds of leaves. Firm, broad leaves float on top of the water, and soft, narrow leaves are found under the water’s surface. A North American species, Canadian pondweed, has stems that grow below the surface and may reach 10 feet (3 meters) in length. Canadian pondweed spreads very rapidly, and has blocked many canals and rivers.
