Alligatorweed, Alternanthera philoxeroides, is a perennial rooted emergent weed. The plant begins its growth rooted in the bottom of the pond, grows up, and emerges from the water.

Narrow sword-like leaves grow off opposite sides of a hollow stem. The stems can vary in color from green to red. This aquatic plant produce small white flowers on the stem. Alligator weed is also known as pigweed or alligator grass.

Native to South America, alligator weed grows in shallow water areas near the shoreline. This aquatic weed can grow as long as four feet in length. While alligator weed is rooted along shorelines, growth spreads at the water surface.

Stems of this invasive plant have nodes from where other stems will grow.

Alligatorweed is an invasive plant and is not native to the United States. This plant grows in thick dense mats along the edges of a pond. The mats make it very difficult for wildlife to reach the shoreline of the pond or lake.

The dense mats can overtake the full shoreline area. This prevents beneficial native plants, plants that wildlife uses for shelter and food, from being able to grow near the edges of the pond. Eventually, these mats will break off from the rooted part of the alligator weed and float freely in the pond.

Alligator weed can be damaging to the overall ecosystem of the pond, affecting both plants and animals. Facilitating the growth of alligatorweed is strongly discouraged as it is an invasive species.

Alligatorweed control can be difficult due to its quick spreading nature. Alligatorweed can be trimmed, but will regrow from roots and stems left behind. If manual removal, maintenance will be necessary repetitively.

Aquatic herbicides are the most effective way to remove Alligatorweed. Herbicides will kill the plant down to the roots, preventing regrowth.

Propeller is the best aquatic herbicide to use for eliminating alligatorweed. Propeller acts rapidly to kill the pond weeds.

Clearcast is another herbicide that can be used to control Alligator weed. Clearcast will act in a slower manner than Propeller. Imazamox is a safer alternative to glyphosate. It is effective on the portions of the weed that are above the surface of the water.

Alligatorweed

• Blooms a white flower
• Produces a hollow stem
• Leaves grow out on opposite sides of the stem

Smartweed

• Leaves come down and wrap around the stem
• Leaves grow out alternate from the stem