apiculatum (Cham.) Asch., and those with no basal spines sometimes distinguished as Ceratophyllum demersum var. Plants with the two basal nut spines very short are sometimes distinguished as Ceratophyllum demersum var. The fruit is a small nut 4–5 mm long, usually with three spines, two basal and one apical, 1–12 mm long. The flowers are small, 2 mm long, with eight or more greenish-brown petals they are produced in the leaf axils. It is monoecious, with separate male and female flowers produced on the same plant. The leaves are produced in whorls of six to twelve, each leaf 8–40 mm long, simple, or forked into two to eight thread-like segments edged with spiny teeth they are stiff and brittle. It is also a popular aquarium plant.Īn aquatic plant, Ceratophyllum demersum has stems that reach lengths of 1–3 m (3–10 ft), with numerous side shoots making a single specimen appear as a large, bushy mass.

It is a harmful introduced weed in New Zealand. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except Antarctica. Ceratophyllum demersum, commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of Ceratophyllum.

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