Callitriche hermaphroditica

Tracheophyta MagnoliopsidaCallitrichaceaeCallitricheCallitriche hermaphroditica


This species occurs in mesotrophic lakes, canals and gravel-pits. It is usually annual, although some populations may perennate. 0-390 m at Drumore Loch (E. Perth).



World Distribution

Circumpolar Boreal-montane element.

Broad Habitats

Standing water and canals

Light (Ellenberg): 7

Moisture (Ellenberg): 12

Reaction (Ellenberg): 7

Nitrogen (Ellenberg): 5

Salt Tolerance (Ellenberg): 1

January Mean Temperature (Celsius): 3.1

July Mean Temperature (Celsius): 13.7

Annual Precipitation (mm): 1120

Length: 50

Perennation - primary


Life Form - primary

Perennial hydrophyte (perennial water plant)



Clonality - primary

Irregularly fragmenting (mainly water plants)

Count of 10km squares in Great Britain: 392

Count of 10km squares in Ireland: 115

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: 0.21

JNCC Designations


Scarce Atlas Account

Scarce Atlas Account: 

Callitriche hermaphroditica L.

Autumnal water-starwort

Status: not scarce


This aquatic species usually grows on silty substrates in mesotrophic or eutrophic lakes. It can be found in shallow water at the edges of sheltered lakes, but in more exposed sites it is confined to deeper water. Species such as Myriophyllum alterniflorum, Potamogeton gramineus, P. x nitens and Nitella flexilis are often found in its more mesotrophic localities, where less frequent associates include Najas flexilis and Potamogeton praelongus. Unlike these scarce species, C. hermaphroditica is also found in abundance in some eutrophic waters, such as the Anglesey lakes, where it can be found with Potamogeton crispus, P. pusillus and Zannichellia palustris. C. hermaphroditica has also been recorded as a colonist of canals and flooded gravel pits. It is a predominantly lowland species, recorded up to 350 metres (Kingside Loch) and 380 metres (Malham Tarn, where its occurrence may have been transient). A record from 425 metres in Perthshire (White 1898) requires confirmation and one from 915 metres in Inverness-shire (McCallum Webster 1978) is erroneous.

C. hermaphroditica is a shallow-rooted annual. The flowers are submerged and pollinated under water. Plants fruit freely. Fruiting plants are often uprooted by autumn winds. Little is known about its germination requirements.

Like many aquatics, C. hermaphroditica was under-recorded in the Atlas of the British Flora (Perring & Walters 1962) and it is difficult to assess any changes in its distribution. There is no evidence to suggest that it has declined, and its tolerance of eutrophication suggests that it is unlikely to be threatened by changes in water quality. In 1985 it was discovered in gravel pits in Lincolnshire, a significant extension of its British distribution.

It is a widespread circumboreal species, occurring in Europe, Asia and North America. In Europe it has a predominantly northern distribution, extending south as far the British Isles, northern Germany and Rumania; it is absent from the Alps.

Although a relatively distinct species, C. hermaphroditica has sometimes been confused with C. hamulata. Many of the records cited by McCallum Webster (1978) are erroneous.


C. D. Preston

Atlas text references

Atlas (151c)
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Martinsson (1991b)
Meusel H, Jäger E, Rauschert S, Weinert E
1978.  Vergleichende Chorologie der zentraleuropäischen Flora. Volume 2. 2 vols.
Preston CD, Croft JM
1997.  Aquatic plants in Britain and Ireland.
Schotsman HD
1967.  Les Callitriches: espèces de France et taxa nouveaux d'Europe.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.