Ceratophyllum demersum

Scientific profile

Ceratophyllum demersum is a perennial, non-woody, herbaceous plant adapted to an aquatic lifestyle. It is rootless, free-floating when young, often settling in the sediment as it matures. The stems, reaching up to around 0.4 m in height, bear whorls of stiff, dark green, finely divided leaves. Leaves are classified as broad-leaved, with an average individual blade area of about 32 mm². Flowers appear from June to September, though they are small and rather inconspicuous. The species is native in Great Britain, occurring in still or slow-flowing, nutrient-rich, calcareous water bodies. It tolerates semi-shade and requires permanently wet or swampy conditions. Ellenberg-type indicator values classify it as a heavy feeder (nitrogen value 8), favouring a basic reaction (value 8), intolerant of salinity (value 0), and experiencing low disturbance (severity 0.27). Diaspore mass is approximately 4.7 mg. On the GB Red List it holds a status of Least Concern (*).