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Ceratophyllum demersum

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About Hornwort (Ceratophyllum demersum) Ceratophyllum demersum, commonly known as hornwort, rigid hornwort, coontail, or coon's tail, is a species of Ceratophyllum. It is a submerged, free-floating aquatic plant, with a cosmopolitan distribution, native to all continents except Antarctica. It is a harmful introduced weed in New Zealand. It is also a popular aquarium plant. Ceratophyllum demersum grows in lakes, ponds, and quiet streams with summer water temperatures of 15-30 degreesC and a rich nutrient status. In North America, it occurs in the entire US and Canada, except Newfoundland. In Europe, it has been reported as far north as at a latitude of 66 degrees in Norway. Ceratophyllum demersum grows in still or very slow-moving water. An 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. 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 monoecious, with separate male and female flowers produced on the same plant. The flowers are small, 2 mm long, with eight or more greenish-brown petals; they are produced in the leaf axils. The fruit is a small nut 4-5 mm long, usually with three spines, two basal and one apical, 1-12 mm long. Ceratophyllum demersum grows in lakes, ponds, and quiet streams with summer water temperatures of 15-30 degreesC and a rich nutrient status.
Plant Description
Plant Type
Perennial herb

Max. Height
3.3 - 9.8 ft (1 - 3 m)


Growth Rate

Flower Color
Blue, Green, Brown

Flowering Season

Native Status

Natural Setting
Elevation ?
-192' - 7775'

Annual Precip. ?
3.0" - 61.1"

Summer Precip. ?
0.15" - 2.49"

Coldest Month ?
28.8° F - 60.1° F

Hottest Month ?
57.6° F - 89.3° F

Humidity ?
0.41 vpd - 43.66 vpd

Soil Description
Adaptable, tolerant of sand, loam and clay

Landscaping Information
Common uses
Bogs and Ponds

Nursery Availability
Never or Almost Never Available

Other Names
Common Names
Rig, Coon's Tail

Sources include: Wikipedia. All text shown in the "About" section of these pages is available under the Creative Commons Attribution-ShareAlike License. Plant observation data provided by the participants of the California Consortia of Herbaria, Sunset information provided by Jepson Flora Project. Propogation from seed information provided by the Santa Barbara Botanical Garden from "Seed Propagation of Native California Plants" by Dara E. Emery. Sources of plant photos include CalPhotos, Wikimedia Commons, and independent plant photographers who have agreed to share their images with Calscape. Other general sources of information include Calflora, CNPS Manual of Vegetation Online, Jepson Flora Project, Las Pilitas, Theodore Payne, Tree of Life, The Xerces Society, and information provided by CNPS volunteer editors, with special thanks to Don Rideout. Climate data used in creation of plant range maps is from PRISM Climate Group, Oregon State University, using 30 year (1981-2010) annual "normals" at an 800 meter spatial resolution.

Links:   Jepson eFlora Taxon Page  CalPhotos  Wikipedia  Calflora

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