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Horned Pondweed

Zannichellia palustris

Please keep in mind that it is illegal to uproot a plant without the landowner's consent and care should be taken at all times not to damage wild plants. Wild plants should never be picked for pleasure and some plants are protected by law.
For more information please download the BSBI Code of Conduct PDF document.


Plant Profile

Flowering Months:
Potamogetonaceae (Pondweed)
Life Cycle:
Maximum Size:
150 centimetres long
Gardens, ponds, water, wetland.

Green, no petals
Male flowers consist of a single stamen. Female flowers occur in groups of up to 5 and have 4 or 5 pistils. The female flower consists of an ovary, a style and a stigma.
The Horned Pondweed is named for the shape of its seed. The seeds are horn-shaped.
An underwater perennial which has stringy-looking, green, thread-like, opposite leaves, up to 8cm long.
Other Names:
Horned Pond-lily, Horned Poolmat.
Frequency (UK):
Occasionally seen  

Other Information


Zannichellia palustris, also known as horned pondweed or horned pond-lily, is a perennial aquatic plant that is native to North America, Europe and Asia. It is commonly found in freshwater ponds, lakes, rivers, and streams. The leaves are long, thin, and typically float on the water's surface, they are lanceolate in shape, with smooth edges and have a distinctive horn-like projections on the leaf base. The stems are long, thin, and anchored to the bottom by rhizomes. The flowers are small and inconspicuous, and arranged in spikes at the top of the stem. They typically bloom in late spring to early summer. It is an important food source for waterfowl and aquatic animals, and it also provides cover and habitat for fish and other aquatic organisms. It's considered a good oxygenator for the aquatic ecosystem and it's also used as an ornamental plant in water gardens and ponds.


Horned pondweed, scientifically known as Zannichellia palustris, is a submersed aquatic plant that belongs to the family Potamogetonaceae. This plant is widely distributed across the Northern Hemisphere and is commonly found in freshwater ecosystems such as ponds, lakes, and slow-moving streams.

Physical Characteristics

Horned pondweed has long, ribbon-like leaves that are usually green in color, but can also appear brownish in some cases. The leaves are slender and can grow up to 25 cm in length. The plant also produces small, greenish-yellow flowers that are enclosed in a thin, tubular sheath. The flowers bloom from June to September and are followed by small, horn-shaped fruits.

Ecological Importance

Horned pondweed plays an important role in maintaining the ecological balance of freshwater ecosystems. The plant provides shelter and breeding grounds for a variety of aquatic organisms, including fish, invertebrates, and amphibians. It also helps to stabilize the sediment and prevent erosion.

Horned pondweed is an important food source for many waterfowl, including ducks and geese. It also serves as a food source for some fish species, such as carp and perch. In addition, the plant is important for nutrient cycling in freshwater ecosystems, as it can absorb and store nutrients from the water column.


Despite its ecological importance, horned pondweed is threatened by a number of factors. Habitat loss and degradation, pollution, and the introduction of invasive species are some of the major threats to this plant. Eutrophication, which is the excessive growth of algae and other aquatic plants due to nutrient pollution, can also pose a threat to horned pondweed by reducing light penetration and reducing the oxygen levels in the water.

Conservation Efforts

Several conservation efforts are underway to protect horned pondweed and other aquatic plants. One such effort is the restoration of degraded wetlands, which can provide habitat for these plants and help to improve water quality. In addition, the removal of invasive species and the reduction of nutrient pollution can also help to protect and preserve these plants.

Horned pondweed is a valuable and important plant in freshwater ecosystems. Its role in providing habitat, food, and nutrient cycling cannot be overstated. While there are threats to the species, conservation efforts are underway to help protect and preserve it for future generations.

More Information about Horned Pondweed

Horned pondweed is also used in some traditional medicines. The plant has been used for treating various health conditions, such as fever, inflammation, and urinary tract infections.

In addition to its ecological and medicinal significance, horned pondweed has some potential uses in the field of bioremediation. Bioremediation is the process of using living organisms to remove pollutants from the environment. Horned pondweed has been found to be effective in removing heavy metals, such as lead and copper, from contaminated water.

Another interesting aspect of horned pondweed is its ability to grow in a wide range of water depths. Unlike some other aquatic plants that are limited to shallow water, horned pondweed can grow in water depths of up to 6 meters, making it an important species in deeper freshwater ecosystems.

Horned pondweed has also been the subject of scientific research due to its unique photosynthetic process. Unlike most plants, horned pondweed can perform a type of photosynthesis called CAM (Crassulacean Acid Metabolism) photosynthesis, which allows it to survive in low light conditions and under water with limited carbon dioxide availability. Understanding the CAM photosynthesis process in horned pondweed can provide valuable insights into improving the efficiency of photosynthesis in other plants, which could have implications for improving agricultural productivity.

Furthermore, horned pondweed is a popular choice for aquarium enthusiasts. Its long, slender leaves make it an attractive addition to aquariums and it can help to provide a natural habitat for fish and other aquatic animals. However, it is important to note that horned pondweed can also grow rapidly and can potentially become invasive in some ecosystems.

Horned pondweed is also a good indicator of water quality. Its presence in a body of water indicates that the water is of good quality, as horned pondweed is sensitive to pollutants and nutrients. However, its absence or decline in numbers can indicate poor water quality, which may be caused by factors such as pollution or eutrophication.

In some cultures, horned pondweed has also been used as a food source. The plant can be cooked or dried and ground into a flour to make bread. While not a common practice in modern times, it highlights the versatility and potential uses of this plant.

In terms of conservation, efforts to protect horned pondweed can have positive impacts on other species and the overall health of freshwater ecosystems. For example, the presence of horned pondweed can increase biodiversity and provide shelter for a variety of aquatic animals, such as small fish and invertebrates. Additionally, healthy populations of horned pondweed can help to maintain water clarity and oxygen levels, which are essential for the survival of aquatic organisms.

Overall, horned pondweed is an important and valuable species in freshwater ecosystems. Its significance extends beyond its ecological and cultural importance to potential industrial applications and scientific research. By protecting and preserving horned pondweed, we can help to maintain the health and diversity of our freshwater ecosystems and ensure the survival of many other species that depend on them.

Distribution Map

Reproduced by kind permission of the BSBI.

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