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Grass-wrack Pondweed

Potamogeton compressus

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Plant Profile

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

Green, 4 petals
Small, green flower spikes.
The fruit are globular capsules, measuring up to 3mm across.
An aquatic perennial species with 5-veined, unstalked, grass-like, sharply pointed leaves. The stems are flattened. Similar in appearance to Blunt-leaved Pondweed (Potamogeton obtusifolius) but with narrower, more pointed leaves and a conspicuous awn. Grows only in still water which is normally limy.
Other Names:
Eel-grass Pondweed, Flatstem Pondweed, Flattened Pondweed.
Frequency (UK):

Similar Species

Other Information


Potamogeton compressus, also known as flattened 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 and are flattened parallel to the stem. 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.


Grass-wrack pondweed, scientifically known as Potamogeton compressus, is a species of aquatic plant that belongs to the Potamogetonaceae family. This plant is found in freshwater lakes, ponds, and rivers across Europe and North America.


The grass-wrack pondweed is a submerged aquatic plant that typically grows up to 2 meters long. The leaves are slender and ribbon-like, and they are arranged alternately along the stem. The leaves are usually dark green in color, and they have distinct veins that run parallel to the length of the leaf. The flowers of this plant are small and unremarkable, and they are produced on spikes that emerge from the water's surface.


Grass-wrack pondweed is a common plant in freshwater habitats, including ponds, lakes, and rivers. It prefers shallow waters with soft substrates, such as mud or sand, and it can tolerate a wide range of water conditions, including low light levels and low oxygen concentrations.

Ecological Importance

Grass-wrack pondweed plays an essential role in freshwater ecosystems. It provides habitat and food for a variety of aquatic animals, including fish, invertebrates, and waterfowl. The plant's dense growth pattern can also provide shelter and protection for juvenile fish and other small aquatic organisms.

Apart from its ecological importance, grass-wrack pondweed is also important for humans. It is used in aquariums and water gardens because of its attractive appearance, and it is also used in the floral industry as a decorative plant.

Threats and Conservation

Like many aquatic plants, grass-wrack pondweed is threatened by human activities such as pollution, habitat destruction, and the introduction of non-native species. Invasive species such as zebra mussels and Eurasian watermilfoil can outcompete and displace native plants like grass-wrack pondweed, reducing the plant's ability to provide habitat and food for aquatic animals.

To protect grass-wrack pondweed and other aquatic plants, it is important to maintain healthy water quality and protect freshwater habitats from pollution and habitat destruction. Additionally, the introduction of non-native species should be carefully managed to prevent the displacement of native plants and animals.

Grass-wrack pondweed is a valuable and important plant in freshwater ecosystems. Its slender leaves and distinctive appearance make it a popular choice for aquariums and water gardens, while its ecological value as a habitat and food source for aquatic animals highlights its importance in maintaining healthy freshwater ecosystems. Protecting and conserving this plant is essential for the long-term health and well-being of freshwater ecosystems and the animals that depend on them.

Facts about Grass-wrack Pondweed

  1. Grass-wrack Pondweed, Potamogeton compressus, is a perennial aquatic plant native to North America and Europe.
  2. The plant is typically found in freshwater lakes, ponds, and slow-moving streams with depths of up to 10 feet.
  3. Grass-wrack Pondweed has long, narrow, ribbon-like leaves that are arranged in a spiral pattern around the stem.
  4. The leaves of the plant can grow up to 10 inches long and are typically bright green in color.
  5. The plant produces small, inconspicuous flowers that are greenish-white in color.
  6. Grass-wrack Pondweed is a dioecious plant, meaning that male and female flowers are produced on separate plants.
  7. The plant can reproduce vegetatively through the growth of rhizomes, or sexually through the production of seeds.
  8. Grass-wrack Pondweed provides important habitat for aquatic animals, including fish, turtles, and waterfowl.
  9. The plant also helps to stabilize sediments and reduce erosion in aquatic environments.
  10. In some cases, Grass-wrack Pondweed can become invasive and outcompete native plant species in aquatic ecosystems.
  11. The plant is tolerant of a wide range of water temperatures and nutrient levels, making it well-suited for colonization in many different aquatic environments.
  12. Grass-wrack Pondweed is also tolerant of low light levels and can grow in shaded areas of lakes and ponds.
  13. The plant can be easily identified by its long, narrow leaves and spiral growth pattern.
  14. Grass-wrack Pondweed is often confused with other similar pondweed species, including curly pondweed (Potamogeton crispus) and sago pondweed (Potamogeton pectinatus).
  15. The best way to control Grass-wrack Pondweed in aquatic environments is through physical removal or the use of aquatic herbicides.
  16. In some cases, the plant may need to be manually removed using rakes or other tools.
  17. It is important to carefully monitor and manage Grass-wrack Pondweed populations in aquatic environments to prevent the plant from becoming invasive.
  18. Grass-wrack Pondweed can be grown in aquaria as an ornamental plant.
  19. The plant requires moderate to high light levels and a nutrient-rich substrate to grow in aquarium environments.
  20. Grass-wrack Pondweed can be propagated by dividing the rhizomes of mature plants or by sowing seeds.
  21. In aquarium environments, Grass-wrack Pondweed can provide important habitat for small fish and invertebrates.
  22. The plant can also help to oxygenate the water in aquariums and reduce nutrient levels.
  23. Grass-wrack Pondweed is a valuable plant for use in wetland restoration and shoreline stabilization projects.
  24. The plant can help to improve water quality and provide important habitat for wildlife in restored wetland areas.
  25. Grass-wrack Pondweed is an important component of many healthy aquatic ecosystems and should be carefully managed to prevent the plant from becoming invasive.

Grass-wrack Pondweed is a native aquatic plant found in freshwater lakes, ponds, and slow-moving streams in North America and Europe. The plant has long, narrow, ribbon-like leaves that are arranged in a spiral pattern around the stem and produces small, inconspicuous greenish-white flowers. It is a dioecious plant that can reproduce vegetatively through rhizomes or sexually through seeds. Grass-wrack Pondweed provides important habitat for aquatic animals and helps to stabilize sediments in aquatic environments. It can become invasive and outcompete native plant species in some cases. The plant can be easily identified by its long, narrow leaves and spiral growth pattern and can be grown in aquaria as an ornamental plant.

Distribution Map

Reproduced by kind permission of the BSBI.

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