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Loddon Pondweed

Potamogeton nodosus

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.
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Plant Profile

Flowering Months:
Potamogetonaceae (Pondweed)
Life Cycle:
Maximum Size:
3 metres long
Ditches, gardens, ponds, water.

Green, 4 petals
A compact, cylindrical flower spike, up to 7cm long. Up to 16 whorls of flowers per spike.
Flower spikes turn reddish-brown when mature, developing into the fruit. The fruit is a narrowly oval dry seed, up to 4.5mm in length.
Broad, lanceolate leaves (up to 15cm long and 4cm wide), both floating and submerged. The leaves are opaque and not net-veined as with Fen Pondweed (Potamogeton coloratus). The narrower submerged leaves are longer and long-stalked. Found in only 3 British rivers: the Berkshire Loddon, the Bristol Avon and the Dorset Stour. Perennial.
Other Names:
Knotted Pondweed, Knotty Pondweed, Longleaf Pondweed, Long-leaved Pondweed.
Frequency (UK):
Rarely seen  

Similar Species

Other Information


Potamogeton nodosus, also known as knotted pondweed, is a perennial aquatic plant that is native to North America. 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. The stems are long, thin, and anchored to the bottom by rhizomes which are knotted or nodose. 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.


Loddon Pondweed, scientifically known as Potamogeton nodosus, is an aquatic plant that is widely distributed across North America, Europe, and Asia. It is a perennial species that grows in freshwater environments such as ponds, lakes, streams, and rivers. This plant is characterized by its narrow, ribbon-like leaves, which are translucent and have a dark green color.

The Loddon Pondweed is a submergent plant, which means that it grows completely underwater. It can reach up to 3 meters in length, and its leaves are around 5-10 cm long and 1-2 mm wide. The plant's stem is smooth, and it can grow up to 2 meters long, making it a perfect hiding place for fish and other aquatic animals.

One of the distinctive features of Loddon Pondweed is the presence of small nodes on the stem that alternate with the leaves. These nodes are bulbous and help the plant to anchor itself to the substrate. The roots of the Loddon Pondweed are thin and white, and they are located at the base of the stem.

The Loddon Pondweed is an important species in freshwater ecosystems. It provides food and shelter for many aquatic animals, including fish, insects, and invertebrates. The plant is also an important source of oxygen for aquatic organisms, as it produces oxygen through photosynthesis.

However, the Loddon Pondweed can become a problem in some areas, where it grows in large numbers and forms dense mats that can impede water flow and block access to recreational areas. In addition, the plant can interfere with water-based activities such as boating and fishing.

To control the growth of Loddon Pondweed, various management strategies are employed, such as mechanical removal and herbicide treatments. However, it is important to carefully manage the plant to avoid disturbing the balance of the ecosystem.

Loddon Pondweed, like other aquatic plants, plays a significant role in maintaining water quality in freshwater ecosystems. It absorbs nutrients such as phosphorus and nitrogen from the water, which can otherwise promote the growth of algae and other unwanted aquatic plants. This process of nutrient uptake, also known as nutrient cycling, helps to maintain the water's clarity and quality.

In addition, Loddon Pondweed has been found to have medicinal properties. The plant contains several bioactive compounds, including alkaloids and flavonoids, which have anti-inflammatory and antioxidant properties. Some studies have shown that extracts from Loddon Pondweed can be effective in treating various diseases such as cancer, diabetes, and cardiovascular diseases.

Loddon Pondweed is also a popular aquarium plant among hobbyists due to its attractive appearance and ease of care. It is relatively easy to cultivate and can be grown in a range of lighting and nutrient conditions.

Despite its many benefits, the Loddon Pondweed, like many other aquatic plants, is facing threats such as habitat loss and degradation due to human activities. Pollution, overfishing, and climate change are all factors that can impact the survival and distribution of the plant.

Therefore, it is important to recognize the value of Loddon Pondweed and other aquatic plants and take measures to protect and preserve their habitats. This can be done through responsible land use practices, pollution control, and conservation efforts. By ensuring the survival of Loddon Pondweed and other aquatic plants, we can help to maintain healthy and diverse freshwater ecosystems for generations to come.

Another important benefit of Loddon Pondweed is its potential as a bioindicator of water quality. Due to its sensitivity to environmental changes, such as water temperature and nutrient levels, the plant can serve as an indicator of the health of the ecosystem. If the Loddon Pondweed is healthy and thriving, it is an indication that the water quality is good. Conversely, if the plant is absent or in poor health, it may indicate that the water quality is degraded.

Additionally, the Loddon Pondweed is an important component of wetland ecosystems, which are vital for flood control, water purification, and wildlife habitat. Wetlands that are rich in Loddon Pondweed and other aquatic plants can provide a range of ecosystem services, including carbon sequestration, erosion control, and groundwater recharge.

Loddon Pondweed is an example of the interconnectedness of living organisms in freshwater ecosystems. The plant relies on other organisms, such as fish and invertebrates, for pollination and dispersal of its seeds. In turn, the plant provides food and shelter for these organisms, creating a complex web of interdependence. By recognizing and valuing the importance of Loddon Pondweed and other aquatic plants, we can promote the conservation and sustainable management of freshwater ecosystems for the benefit of all living organisms.

Loddon Pondweed also has cultural significance in some regions. In some Indigenous cultures, the plant has been traditionally used for medicinal purposes and as a source of food. The plant's roots and leaves were believed to have healing properties and were used to treat various ailments, including headaches, sore throats, and skin conditions. The seeds of Loddon Pondweed were also used as a source of food, and were ground into flour to make bread.

The plant has also been used in traditional ecological knowledge systems, which are a way of understanding the natural world based on observation and experience. Indigenous communities have observed the behavior of Loddon Pondweed and other aquatic plants over generations, and this knowledge has been passed down through oral traditions. This traditional ecological knowledge is valuable for understanding the interconnections between different species and their roles in the ecosystem.

In conclusion, Loddon Pondweed, also known as Potamogeton nodosus, is a valuable and important species in freshwater ecosystems. It provides food and shelter for aquatic animals, contributes to water quality, has medicinal properties, and has cultural significance. By recognizing and valuing the importance of Loddon Pondweed and other aquatic plants, we can promote the conservation and sustainable management of freshwater ecosystems for the benefit of all living organisms.

Distribution Map

Reproduced by kind permission of the BSBI.

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