The Water Weed From Hell

By James Donahue

At first glance, the aquatic plant salvina molesta is pleasant to look at. Its thick, pale green foliage was chosen by some unsuspecting nurseries and aquarium retailers because of its vigor under almost any condition. Just add water and it grows.

Its origins are Brazil. In their silent and unthinking quest to turn a profit, the people who marketed salvina as a decorative addition to home aquariums, managed to peddle this weed all over the world.

They unleashed a monster.

The plant now grows unchecked in lakes, streams, ponds and ocean fronts all over the Southern United States and in similar places all over the world. It chokes out all other plants, kills fish and other aquatic creatures, doubles its numbers in only four days, and seems to have few, if any, natural enemies.

Throughout Asia, Japan and the rice producing nations of the world there is great concern. The plant threatens to destroy the rice by taking over the rice fields. Rice grows in water.

Salvina molesta floats free in the water. It has two folded, hairy pads, or leaves that emerge from the water and a feathery root-like structure hanging down from there. A cluster of salvina molesta forms dense mats of vegetation on the surface of the water that prohibits any other plant or species from co-existing.   

A U. S. Army Corps of Engineers bulletin identifies salvina molesta as the worlds worst weed.

The bulletin said that since 1997, when first found in North Carolina, the weed has spread at an alarming rate. It now is in Hawaii, Alabama, Texas, Mississippi, South Carolina, Louisiana and Florida.

Flushing just one plant into an inland lake literally destroys that lake for recreational or beachfront purposes within months. One plant can increase to 8,000 within the first month. After two months there are 67,000,000 plants. After four months, the number increases to 4,500,000,000,000,000.

Smashing the foliage with paddles or driving a boat into a mat of salvina only helps it reproduce. Pieces of this plant continue growing into adults. Collectively salvina grows in large, thick mats that float on the surface of the water.

Under the mat lies dying or dead vegetation that continues to accumulate as new plants emerge on the surface. Mats of salvina have been found as large as 96 square miles and up to three feet deep. They become so thick they block all sunlight from penetrating the infested water, choking out all other aquatic life. The decaying plants decrease the amount of oxygen in the water.

It is believed that salvina has been spread by aquarium owners and water gardeners who carelessly throw the plants away after they get too large for the home tanks. Flushing into old septic systems that drain into nearby lakes and streams, or simply throwing them into a ditch does not kill salvina.

The plant is an amazing survivor. It lives to take up residence where ever it is tossed. All it needs is water.