Ceratophyllum submersumL.

Soft Hornwort

WFO wfo-0000832288 Accepted WFO 2026-06 8 photographs CC BY / CC BY-SA

Plate 1 figs. a–h · 8 separate observations

Ceratophyllum submersum, photographed by J. Drzewiecka
fig. a J. Drzewiecka, CC BY 4.0 / 2022-04-30 / obs. 192489623

Every figure is a research-grade observation under CC0, CC BY or CC BY-SA, rehosted with the photographer’s name, the licence and the observation it came from. Photographs under a NonCommercial licence are excluded from this site and are never stored, which costs us a great many pictures and is not negotiable.

Native range 52 botanical countries

Regions where Ceratophyllum submersum is native: Algeria, Cameroon, Chad, DR Congo, Guinea, Kenya, Libya, Morocco, Nigeria, Tanzania, Tunisia, Altay, Kazakhstan, Kirgizstan, North Caucasus, Oman, Palestine, Türkiye, Uzbekistan, West Siberia, Bangladesh, India, Albania, Austria, Baltic States, Belarus, Belgium, Bulgaria, Central European Russia, Corse, Czechia-Slovakia, Denmark, East European Russia, France, Germany, Great Britain, Greece, Hungary, Ireland, Italy, Krym, Netherlands, Northwest European Russia, NW. Balkan Pen., Poland, Romania, Sicilia, South European Russia, Spain, Sweden, Switzerland, Ukraine AlgeriaCameroonChadDR CongoGuineaKenyaLibyaMoroccoNigeriaTanzaniaTunisiaAltayKazakhstanKirgizstanNorth CaucasusOmanPalestineTürkiyeUzbekistanWest SiberiaBangladeshIndiaAlbaniaAustriaBaltic StatesBelarusBelgiumBulgariaCentral European RussiaCorseCzechia-SlovakiaDenmarkEast European RussiaFranceGermanyGreeceHungaryIrelandItalyKrymNetherlandsNorthwest European RussiaNW. Balkan Pen.PolandRomaniaSiciliaSouth European RussiaSpainSwedenSwitzerlandUkraine
Native distribution of Ceratophyllum submersum, after Kew’s World Checklist of Vascular Plants. Introduced, extinct and doubtful records are excluded, so this is where the plant is from, not everywhere it now grows.
RegionTDWG codeContinent
Albania ALB EUROPE
Austria AUT
Baltic States BLT
Belarus BLR
Belgium BGM
Bulgaria BUL
Central European Russia RUC
Corse COR
Czechia-Slovakia CZE
Denmark DEN
East European Russia RUE
France FRA
Germany GER
Great Britain GRB
Greece GRC
Hungary HUN
Ireland IRE
Italy ITA
Krym KRY
Netherlands NET
Northwest European Russia RUW
NW. Balkan Pen. YUG
Poland POL
Romania ROM
Sicilia SIC
South European Russia RUS
Spain SPA
Sweden SWE
Switzerland SWI
Ukraine UKR
Algeria ALG AFRICA
Cameroon CMN
Chad CHA
DR Congo ZAI
Guinea GUI
Kenya KEN
Libya LBY
Morocco MOR
Nigeria NGA
Tanzania TAN
Tunisia TUN
Altay ALT ASIA-TEMPERATE
Kazakhstan KAZ
Kirgizstan KGZ
North Caucasus NCS
Oman OMA
Palestine PAL
Türkiye TUR
Uzbekistan UZB
West Siberia WSB
Bangladesh BAN ASIA-TROPICAL
India IND

Not drawn on the map: Great Britain. We hold no public-domain boundary for this region, so it is listed rather than guessed at.

Region boundaries approximated from Natural Earth (public domain) and mapped to TDWG World Geographical Scheme for Recording Plant Distributions (WGSRPD) level-3 botanical countries (Brummitt 2001). Indicative, not the official WGSRPD geometry.

Where it actually grows measured, from 166 observations

Condition 5th percentile Median 95th percentile
Coldest month, mean daily low -18.8 °C -4.0 °C 3.4 °C
Warmest month, mean daily high 19.8 °C 23.4 °C 28.9 °C
Annual rainfall 353 mm 621 mm 866 mm
Rainfall in the driest quarter 56 mm 108 mm 163 mm

It is found where winters are severely cold. This is not care advice and it is not a forecast. It is a measurement: we sampled the climate at every one of the 166 research-grade observations of Ceratophyllum submersum that carry a coordinate, and this is the range those places actually span. The 5th and 95th percentiles are used rather than the minimum and maximum, because a single cultivated specimen in a heated conservatory should not widen a tropical plant's range to the Arctic.

This is not a hardiness zone. A USDA zone is the average annual extreme minimum temperature. The figure above is the mean daily minimum of the coldest month, which is a different quantity and is typically far warmer. Reading one as the other would place a plant several zones too warm, so we do not publish a hardiness zone, because we do not have one.

Also published as 13 synonyms

A synonym is not an error. It is a record of botanists disagreeing, in print, about where this plant belongs. Each of these was somebody’s considered answer.

  • Ceratophyllum demersum var. laeve Crép.
  • Ceratophyllum granulosum Schur
  • Ceratophyllum haynaldianum Borbás
  • Ceratophyllum inerme Dumort.
  • Ceratophyllum laeve Lam.
  • Ceratophyllum muticum Cham.
  • Ceratophyllum submersum subsp. submersum
  • Ceratophyllum submersum subvar. muticum Nyman
  • Ceratophyllum submersum var. granulosum (Schur) Nyman
  • Ceratophyllum submersum var. inerme Van Haes.
  • Ceratophyllum submersum var. spinosum Mérat
  • Ceratophyllum verrucosum Gray
  • Ceratophyllum verruculosum Rich.

Sourcesevery claim on this page

  1. World Flora Online Plant List. accepted name, authority, classification. CC0. Retrieved 2026-07-12.
  2. iNaturalist. photographs and flowering annotations, CC0 / CC BY / CC BY-SA only. per photograph. Retrieved 2026-06-27.
  3. Wikidata. common name (P1843), joined on the World Flora Online identifier (P7715). CC0. Retrieved 2026-07-13.
  4. Kew, World Checklist of Vascular Plants (WCVP v16). native distribution by TDWG level-3 botanical country, and life form. CC BY 3.0. Retrieved 2026-06-04.

We publish what we can source and we say so when we cannot. This page has no care advice and no toxicity claim, because we do not yet have those from a source we can cite.