Waterthread Pondweed

Biological Name:

Persicaria amphibia (Waterthread-Pondweed)

Natural Habitat:

Waterthread-Pondweed is a type of aquatic plant that is native to wetlands, marshes, and other areas with standing water in temperate regions of the world, such as Europe and North America. It is commonly found in shallow water and can grow in a variety of soil types, including sandy or clayey soils.


Waterthread-Pondweed is an aquatic plant that is native to North America. It has long narrow leaves and small inconspicuous flowers. It is often found in still or slow-moving water and is used in wetland restoration projects.

Frequently Asked Questions (FAQs)

Q: What kills floating leaf pondweed?
A: Our top recommended products to treat pondweed is Diquat Herbicide. Diquat Herbicide is labeled to control Pondweed (except for Richardsons pondweed) and has shown to do a great job against it. Diquat also carries a wide label so it can kill a large number of other unwanted aquatic weeds you may be dealing with too.

Q: Can you use RoundUp on pond weeds?
A: RoundUp®, a commonly used glyphosate herbicide is not approved for use in ponds. There are other glyphosate herbicides which are approved for aquatic sites. The difference lies in additional ingredients in RoundUp®, making it more toxic to certain kinds of aquatic life.

Q: How do you control floating weeds?
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Q: How do I get rid of pondweed in my pond?
A: Duckweed is very small, and thus can be raked, vacuumed, or skimmed from the water’s surface without much effort. Simply adding more aeration to your pond to promote more water movement will also help prevent some floating weeds from being able to establish, as they typically prefer still water.

Q: How do I get rid of duckweed in my pond naturally?
A: Duckweed prefers to grow in water that is stagnant or extremely slow-moving. To rid your water of a duckweed problem, you can try aerating it. Using bubble aeration will discourage growth and kill duckweed plants that have already grown. Aerating a pond can also help reduce any foul odors associated with the water.

Q: What kills pond algae naturally?
A: Hydrogen peroxide is a common treatment for algae overgrowth in backyard ponds. If you’re struggling with algae, particularly string algae on rocks or waterfalls, then hydrogen peroxide could be an effective natural solution.

Q: Can you eat sago pondweed?
A: All parts of the plant are eaten but the seeds and tubers are especially nutritious. Sago pondweed also provides habitat for invertebrates which are food for birds, especially young waterfowl.

Q: Are sago plants poisonous to humans?
A: Sago palm is known to be poisonous and sago separation includes careful processes to remove these toxins, before they are edible. Intake of sago before proper processing to remove toxins can cause vomiting, liver damage, and even death.

Q: Should I remove pondweed?
A: A small amount of algae or pondweed is beneficial to ponds, providing food for tadpoles and other water creatures, but too much can block light from submerged plants and prevent them from photosynthesising, reducing oxygen levels in your pond.

Q: Is pondweed good for compost?
A: When the time is up, don’t let the dried-out remains go to waste. Compost it. Old water weed is the best natural compost activator ever and it’s entirely free, so make the most of your natural harvest.

Q: What is the purpose of pondweed?
A: Ecological Importance. Sago pondweed is an extremely important aquatic plant in lakes and ponds because of its nutritional value as a food source for birds, including waterfowl (especially diving ducks and swans), marsh birds, and shorebirds.

Q: Is pondweed an invasive plant?
A: Curly-leaved Pondweed is a hardy, aggressive non-native invasive plant. The oblong light to dark green leaves are distinctly serrated, wavy, and typically 3” long.

Q: Why do we put pondweed in a fish tank?
A: An aquatic pondweed used in home aquarium tanks as both an ornamental and oxygenating plant.

Q: What type of aquatic plant is pondweed?
A: Potamogeton is a genus of aquatic, mostly freshwater, plants of the family Potamogetonaceae. Most are known by the common name pondweed, although many unrelated plants may be called pondweed, such as Canadian pondweed (Elodea canadensis).

Q: Why is pondweed important?
A: Pondweeds provide food and habitat for aquatic animals and are an important food source for waterfowl. The pondweeds that occur in this area are mainly found in still or slow moving freshwater, although some are tolerant of brackish conditions.

Q: Does pondweed need light?
A: To do this job, the pond weed needs energy. It gets this from the light which shines on it. Bright light provides more energy than dim light. Red light is more easily used by the pond weed than most other colours.

Q: Do fish eat pondweed?
A: Grass carp love to eat weeds such as eloda, hydrilla, naiads, parrotfeather, and pondweeds. Bushy pondweed, American pondweed, and hydrilla are preferred vegetation. Grass carp are not effective for bulrush, filamentous algae (pond scum or moss), water primrose, coontail, Eurasian milfoil, or cattails.

Q: Who eats pondweed?
A: American pondweed is often a food source for fish, waterfowl and turtles.

Q: How do you keep pondweed alive?
A: Pondweed is best kept in a a constantly aerated tank (just use a simple aquarium pump) filled with tap water located near a window or with a bright lamp (>1200lm). Putting pondweed into cold water straight from the tap may cold shock it so take care to allow water to come to room temperature.

Q: What kills large leaf pondweed?
A: Chemical Control The products that have been successful in treating large leaf pondweed individually or in combination are Reward and Weedtrine D, Aquathol K – liquid, Aquathol Super K – granular, Propeller, and Sonar AS and Sonar RTU.

Q: How can I control my pond weeds cheaply?
A: Some weeds are best treated with a granular herbicide like Cutrine Plus when weeds are submerged as blankets under the water surface, in deep areas of the pond, or in ponds with flowing water. These heavier granules can be applied with a hand spreader and will sink directly onto the weed beds.

About the author

Samuel is a gardening professional and enthusiast who has spent over 20 years advising homeowners and farm owners on weed identification, prevention and removal. He has an undergraduate degree in plant and soil science from Michigan State University.