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Rigid Hornwort

Ceratophyllum demersum

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Plant Profile

Flowering Months:
Ceratophyllaceae (Hornwort)
Also in this family:
Life Cycle:
Maximum Size:
3 metres long
Ditches, ponds, water.

Green, many petals
The minute, green flowers have 8 or more petals. It is a shy-flowerer. Male flowers are whitish and females are green. Pollinated by water.
Smooth and warty, beaked fruit. The fruit has 2 spines at the base. The similar looking Soft Hornwort (Ceratophyllum demersum) does not have these spines.
The feathery leaves are compact and thread-like, growing in whorls of 5 to 14. They fork off from the main stem 1 or 2 times. The jointed stems have a reddish tinge to them. Perennial.
Other Names:
Coon's-tail, Coontail, Hornwort.
Frequency (UK):
Occasionally seen  

Similar Species

Other Information


Ceratophyllum demersum, also known as coontail or hornwort, is a submerged aquatic plant that is commonly found in freshwater environments such as ponds, lakes, and rivers. It is a hardy, fast-growing species that can tolerate a wide range of water conditions, including both clear and murky waters. It has thin, branched, green stems that can grow up to 3 meters long, with small, inconspicuous flowers. It is often used as an oxygenating plant in aquaria and as a food source for some aquatic animals. In addition, it can also be used to help control algae growth and for water purification.


Rigid Hornwort, also known as Ceratophyllum demersum, is a species of aquatic plant that is commonly found in freshwater environments around the world. It is often used in aquariums and water gardens, and is known for its unique appearance and ability to improve water quality.

Appearance and Characteristics

Rigid Hornwort is a submerged aquatic plant that typically grows to be 1-3 meters in length. It has a distinctive appearance, with whorls of bright green, needle-like leaves that are arranged in a circular pattern around the stem. The leaves are quite rigid and brittle, and break easily when handled. The plant also has small, inconspicuous flowers that bloom above the water's surface.

Ceratophyllum demersum is a fast-growing plant that can quickly spread and cover large areas of water. It is able to grow in a variety of conditions, including still or moving water, and can tolerate a range of water temperatures and nutrient levels.

Ecological Importance

Rigid Hornwort is an important plant in aquatic ecosystems, as it provides a range of benefits to both plants and animals. The plant's dense growth can provide shelter and hiding places for fish and other aquatic animals, and can also serve as a food source for certain herbivorous fish species.

In addition to its ecological benefits, Rigid Hornwort is also used in water treatment applications. The plant is able to absorb nutrients and other pollutants from the water, helping to improve water quality and reduce the risk of algal blooms.

Aquarium and Water Garden Use

Rigid Hornwort is a popular choice for aquariums and water gardens due to its unique appearance and ease of care. The plant is able to thrive in a variety of conditions, and is able to absorb excess nutrients from the water, helping to keep the tank or pond clean.

In aquariums, Rigid Hornwort can be used to provide a natural-looking background or as a floating plant. It can also serve as a hiding place for fish and other aquatic animals, and can help to reduce stress levels by providing a sense of security.

In water gardens, Rigid Hornwort can be used to add texture and visual interest to the pond, and can also help to improve water quality by absorbing excess nutrients.

Care and Maintenance

Rigid Hornwort is a relatively low-maintenance plant that requires minimal care. It is able to grow in a variety of conditions, but prefers bright, indirect light and a pH level between 6.5 and 7.5. The plant does not require any special fertilizers, but can benefit from the addition of a liquid aquarium plant fertilizer.

When handling Rigid Hornwort, it is important to be gentle, as the leaves are quite brittle and can break easily. The plant can be propagated by taking cuttings and planting them in the substrate or floating them on the surface of the water.

In conclusion, Rigid Hornwort is a unique and versatile aquatic plant that provides a range of benefits to both plants and animals in aquatic environments. Whether you are looking to add a natural touch to your aquarium or improve water quality in your pond, Rigid Hornwort is an excellent choice that is sure to thrive with minimal care.

Blog continuation...

Rigid Hornwort is a plant species that belongs to the Ceratophyllaceae family. It is native to Europe, Asia, and North America and can be found in a variety of freshwater habitats, including lakes, ponds, streams, and rivers.

One of the reasons that Rigid Hornwort is so popular in aquariums and water gardens is that it is an excellent oxygenator. The plant releases oxygen into the water through tiny bubbles that form on its leaves. This helps to maintain healthy oxygen levels in the water, which is essential for the health of fish and other aquatic animals.

In addition to its oxygenating properties, Rigid Hornwort is also a good choice for aquarists and water gardeners who are looking for a plant that can help to control algae growth. The plant absorbs nutrients from the water, which can help to reduce the amount of nutrients available to algae, thereby helping to prevent the formation of unsightly and potentially harmful algae blooms.

When used in an aquarium or water garden, Rigid Hornwort should be planted in a substrate or allowed to float freely on the surface of the water. The plant does not require any special lighting or heating, but will grow faster and healthier with moderate to high lighting and a water temperature between 60-80°F (15-26°C).

While Rigid Hornwort is a hardy plant that can tolerate a range of water conditions, it is still important to monitor water quality and perform regular water changes to maintain a healthy and stable aquatic environment.

In addition to its ecological and aesthetic benefits, Rigid Hornwort also has medicinal properties. It has been used for centuries in traditional medicine to treat a variety of ailments, including digestive issues, respiratory problems, and skin conditions.

The plant contains a range of bioactive compounds, including tannins, flavonoids, and alkaloids, which are believed to be responsible for its medicinal properties. Some studies have shown that Rigid Hornwort has anti-inflammatory, antioxidant, and antimicrobial properties, which may make it effective in treating a range of health conditions.

However, it is important to note that while Rigid Hornwort has been used in traditional medicine for centuries, more research is needed to fully understand its medicinal properties and potential side effects. As with any herbal supplement or treatment, it is important to consult with a healthcare professional before using Rigid Hornwort for medicinal purposes.

In some areas, Rigid Hornwort is considered an invasive species, as it can quickly spread and displace native plant species. If you are considering adding Rigid Hornwort to your aquarium or water garden, it is important to ensure that it is legal to do so in your area, and to take steps to prevent the plant from escaping into natural waterways.

Overall, Rigid Hornwort is a fascinating and versatile plant that provides a range of benefits to both humans and aquatic ecosystems. Whether you are looking to improve water quality, provide a natural habitat for fish and other aquatic animals, or explore its potential medicinal properties, Rigid Hornwort is a plant that is well worth considering.

Distribution Map

Reproduced by kind permission of the BSBI.

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