Water Lettuce Pond Plants

Habitat

• Water lettuce plants grow throughout the southeast U.S., but they are also found in Arizona, California, Texas and Hawaii. The plants appear as far north as New Jersey and New York despite claims that cold weather limits their spread. The plants grow in canals, ditches and anywhere they can find slow-moving water.

Features

• As the name implies, water lettuce plants resemble floating lettuce heads. They form rosettes of thick, green leaves with fine hairs and prominent veins. The plants develop white flowers but they are hidden in the rosettes. The light-colored roots grow up to 20 inches long and have a feathery texture.

Growth

• Some water lettuce plants form seedlings in mild climates. Others sprout daughter plants from stem-like stolons. The plants interlink to create large, floating mats that cover entire ponds, clog storm drains and obstruct river traffic. The floating mats reduce the amount of oxygen in the water, which in turn kills fish. Eventually, they disturb the balance of ecosystems and interfere with boating, fishing and swimming.

Control

• Mechanical control options involve clearing the water lettuce pond plants with a rake. Chemical control options include algaecides and herbicides. Liquid diquat formulas contain both algaecides and herbicides that kill pond plants on contact. Liquid penoxsulam and glyphosate formulas are broad spectrum, systemic herbicides that kill plants slowly. Exercise caution with chemical treatments as aquatic herbicides deplete oxygen levels and inadvertently kill fish.