What is Ceratophyllum?

Ceratophyllum refers to a genus of plants commonly known as the hornworts, and sometimes called coontails. They are aquatic plants and grow floating under water, often close to the surface. They are usually green, with needle-like leaves. They are found all over the world in temperate and tropical climates growing in freshwater habitats. They are also cultivated for use in garden ponds and in aquariums, where they can help to keep the water clear.

Most types of ceratophyllum are bright green, although some varieties are a darker olive green shade. The stems are smooth and delicate, often branching out in a few spots, and can grow to a length of 3 to 10 feet (1 to 3 m) in optimal conditions. The long, narrow, flat leaves that resemble pine needles grow in all directions around the stem along its entire length, with denser growth near the tip. Ceratophyllum usually floats freely in the water and has no roots, although occasionally it will grow root-like leaves that will help anchor the plant in moving water. Tiny green flowers that are located near the base of the leaves bloom during the summer months, often unnoticed.

The native distribution of ceratophyllum is referred to as cosmopolitan, which means that it is found all over the world and doesn't have a specific native area. It prefers tropical and temperate climates. It is found in fresh water ponds, lakes, marshes, and slow moving streams, most often floating underwater close to the surface. It is also cultivated in man-made garden ponds, and used in aquariums.

The main requirements for ceratophyllum to grow are sunlight and water. Although they do produce seeds, ceratophyllum usually multiplies by division. When pieces of the plant break off due to the delicate nature of the stem, they frequently grow to form new plants, also known as regenerating. When used as a pond plant, a gardener just has to gently break off the tips of the plant and let them float if more plants are desired. Under the right conditions, the plant will usually multiply without assistance, and may even start to fill the whole pond and need thinning out.

Ceratophyllum is often placed in garden ponds or aquariums to help keep the water clear of algae. It grows extremely quickly and uses up the nutrients in the water, essentially starving out the algae growth. It consumes any extra nitrates in the water and gives off large amounts of oxygen, helping to maintain a healthy aquatic environment. It also provides shelter for small fish and invertebrates like snails, making it a useful habitat plant in both natural and man-made settings.