Isoetes echinospora

Tracheophyta LycopodiopsidaIsoetaceaeIsoetesIsoetes echinospora


A submerged aquatic perennial usually found in nutrient-poor lakes over a wide range of substrates, from rocks and stones to silt and peat. It also grows in more mesotrophic water, such as coastal lakes enriched by wind-borne base salts, lowland reservoirs, slow-flowing rivers and flooded gravel- and clay-pits. It often grows with I. lacustris, and not infrequently hybridises with it. 0-500 m (Loch Callater, S. Aberdeen).



World Distribution

Circumpolar Boreal-montane element, with a disjunct distribution.

Broad Habitats

Standing water and canals

Light (Ellenberg): 7

Moisture (Ellenberg): 12

Reaction (Ellenberg): 5

Nitrogen (Ellenberg): 2

Salt Tolerance (Ellenberg): 0

January Mean Temperature (Celsius): 3.2

July Mean Temperature (Celsius): 13

Annual Precipitation (mm): 1613

Length: 15

Perennation - primary


Life Form - primary

Perennial hydrophyte (perennial water plant)



Clonality - primary

Little or no vegetative spread

Count of 10km squares in Great Britain: 178

Count of 10km squares in Ireland: 32

Count of 10km squares in the Channel Isles: 0

Atlas Change Index: 0.65

JNCC Designations


Scarce Atlas Account

Scarce Atlas Account: 

Isoetes echinospora Durieu

Spring quillwort

Status: scarce



This is a submerged aquatic pteridophyte which forms open stands to a depth of 2 metres in mountain and moorland lakes on acid, gravelly, usually nutrient-poor substrates. It is associated with a few other macrophytes, e.g. Littorella uniflora, Lobelia dortmanna, Potamogeton gramineus and Subularia aquatica, but it usually grows in deeper water than the first two species. Occasionally it is found with filamentous green and blue-green algae. It is found from sea-level at Little Sea in shallow lagoons on sand in which Potamogeton obtusifolius and Nitella sp. are associates, to 500 metres at Loch Callater. 

Plants of I. echinospora are perennial. Copious spores mature in the autumn at the leaf-bases and embed in the tight rosette. They are only distributed when plants are dislodged by wave action or by fish or birds, and then washed up on the strand line or moved by water contents or birds.

The increase in records since 1962 may reflect acidification of upland lake waters, but is more likely to be the result of more active botanical recording. There is the risk that pasture improvement by fertilisers or lime will, through eutrophication, increase competition by other plants to the detriment of I. echinospora.

It is a widespread plant in Scandinavia and in Iceland hut rare and scattered in Europe south of 55 °N where it is threatened by eutrophication. Its European distribution is mapped by Jalas & Suominen (1972). It is a boreal species found across northern Asia (often under other names), and common in North America south to Pennsylvania and north California.

The ecology of this species has been discussed by Seddon (1965), but its absence or rarity in some areas where rock substrates appear suitable is an anomaly still to be studied and may be correlated with water temperatures and chemistry in early Pleistocene Britain.



A. C. Jermy

Atlas text references

Atlas (2d)
Hultén E, Fries M
1986.  Atlas of north European vascular plants north of the Tropic of Cancer. 3 vols.
Jalas & Suominen (1972)
Bangerter EB, Cannon JFM, Jermy AC
1978.  Ferns and their allies. The Island of Mull: a survey of its flora and environment. :12.1-12.7.
Meusel H, Jäger E, Weinert E
1965.  Vergleichende Chorologie der zentraleuropäischen Flora. Volume 1. 2 vols.
Page CN
1997.  The ferns of Britain and Ireland, edn 2.
Preston CD, Croft JM
1997.  Aquatic plants in Britain and Ireland.
Stewart A, Pearman DA, Preston CD
1994.  Scarce plants in Britain.