Freshwater Aquatic Plants With Inflated Leaf Stems

Water Chestnut

• Water chestnut (Trapa natans) is a rooted aquatic plant with triangular, saw-toothed leaves about an inch long. These leaves are attached to a long stem up to 16 feet long by an inflated petiole approximately 6 inches long. The inflated petiole adds buoyancy to the leaves. Water chestnut features a small white flower in the early summer. This aquatic plant is native to Africa, Asia and Europe but is invasive in the United States, where it can create a dense mat that crowds out native organisms.

Water Hyacinth

• Water hyacinth (Eichhoria crassipes) is a free-floating aquatic plant native to South America but found throughout much of the southern United States. This plant can grow up to 3 feet tall; features attractive, light blue to violet flowers on a terminal spike; has a thick, fibrous root system; and has dark green circular leaves attached to an inflated petiole. Water hyacinth has an aggressive habit and can form thick, oxygen-depleting mats.

Bladderwort

• Multiple species of bladderwort, including big floating bladderwort (Utricularia inflata) and little floating bladderwort (Utricularia radiata), are free-floating plants that have small bladders attached to stems. These bladders trap and digest tiny animals, from which the bladderwort obtains nutrients. Big floating bladderwort produces yellow, snapdragon-like flowers but reproduces from small fragments rather than seed. In addition to the floating bladders and showy flowers, this plant can be identified by a spoke-like structure that supports the flower stalk.

Water Smartweed

• Water smartweed (Polygonum apmphibium) is a rooted aquatic plant with floating leaves that grows approximately 3 feet tall. This plant has jointed stems that are swollen at the nodes. Both floating and submerged stems are often inflated. Water smartweed leaves grow up to 6 inches long and are rounded or heart-shaped, with sheathes at the leaf base that have stiff hairs. This aquatic plant produces small, bright pink flowers on a terminal spike that mature into dark nutlets. Water smartweed is generally found in tidal waters, inland waters or even wet soil.

Specialized Gas-Conducting Tissue

• A broad range of aquatic plants have aerenchyma, or large air spaces in the petiole that run from the leaf, where air is available, to the submerged stem and root that cannot capture air. Young leaves possess a pressure gradient that forces air to the roots. Older leaves lose the ability to pressurize air, so spent gases from the roots escape through the aged foliage.