Ceratophyllum demersum.fr.wikipedia.org. (Accessed 5/2014).

Ceratophyllum demersum is a submersed, rootless aquatic perennial herb, stems thin, long, branched, branches often modified into root-like rhizoids.

Leaves in numerous whorls of 5-12, 1-3 cm long, to 0.1 cm wide, linear, somewhat stiff, usually forked once or twice into 2-4 segments, one side with sparse, back curved teeth.

Flowers inconspicuous, sexes separate, axillary, males above female, surrounded by 8-10 bracts (sepals) fused at base, 0.1-0.2 cm long .

Fruit 1-seeded (achene) 0.4-0.6 cm long spine tipped and with two basal spines.

Wetland status: OBL.

Frequency in NYC: Infrequent

Origin: Native.

Habitat: Still, open water of ponds or slow rivers and streams; pH 6.2-8.3 (USDA 2006).

Notes: Can be quite aggressive in warm, nutrient rich water. Often mixed with milfoil, Myriophyllum spp.(USACE 2002).