Great tassel stonewort (Tolypella prolifera)

Great tassel stonewort in water
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Great tassel stonewort fact file

Great tassel stonewort description


Stoneworts used to be classified as members of the plant kingdom, but it is now agreed that they belong, along with other green algae, in the kingdom called Protista. Put simply, the protistas are simple multi-celled or single celled organisms, descended from some of the earliest life-forms that appeared on Earth. Some of the Chlorophytes, specifically the stoneworts, are thought by scientists to have been the early ancestors of all plants. Stoneworts do indeed resemble plants, are frequently mistaken for them, and are often found as fossils. The main body of the plant consists of a series of 'giant cells' up to several centimetres in length, which effectively makes up the stem, together with branches resembling leaves radiating out from nodes that are made up of smaller cells. The stonewort anchors itself, not with roots like a plant, but with rhizoids, colourless, hair-like filaments. Like roots, these can absorb nutrients, but the organism can absorb and breathe through its entire surface. They live in fresh or brackish water, which is low in nutrients and many species require water that is high in calcium. Stoneworts are often encrusted with white lime deposits, giving a crusty texture (hence the name 'stonewort'), and they often have an unpleasant smell, similar to stale garlic.

This is a large stonewort, with stems up to 40cm long. It has whorls of branches, some of which are short and 'incurved', that is bending back towards the stem. These form dense, ball-like heads. The stem between the whorls is formed from a single cell. These are amongst the largest cells of any organism, sometimes reaching 20cm in length and 3mm in diameter.

Stem length: up to 40cm

Great tassel stonewort biology

This species is a summer annual that requires open conditions to grow. It appears a year or two after dredging operations, and then remains dormant until the next clearance.


Great tassel stonewort range

Great tassel stonewort has a scattered range across central western Europe, as far north as Poland and south to northern Italy, and is also known from North and South America. England seems to mark its northern limit, where it has been recorded as far north as Lancashire and Yorkshire. However, since 1970 it has only been found at nine sites, three in Cambridgeshire, one in Lincolnshire, two in Somerset and three in Sussex.


Great tassel stonewort habitat

Great tassel stonewort is an aquatic species of clean water ditches, with an alkaline pH. It is associated with plants such as whorled milfoil, water violet and fan-leaved water crowfoot.


Great tassel stonewort status

Classified as Endangered in the UK, and protected under the Wildlife and Countryside Act, 1981 as amended.


Great tassel stonewort threats

The main threat to this species is enrichment of the water by agricultural run-off. Lack of disturbance could also pose problems, but this is normally a part of routine ditch management.


Great tassel stonewort conservation

Great tassel stonewort is listed as a priority species in the UK Biodiversity Action Plan (UK BAP), and is included in English Nature's Species Recovery Programme. Plantlife have also included this species in their 'Back from the Brink' project. A number of initiatives have been taking place to conserve this species and other members of the stonewort family. These involve ensuring its protection at the current sites, and monitoring the movement of nutrients through the ditch networks. The family has also been the subject of a profile-raising programme for managers of the sites where it occurs, hopefully ensuring that stoneworts remain at these sites. However, in order for the species to increase their UK populations, a viable spore bank has to be present. Surveys following ditch clearance work have discovered new populations, suggesting that there are spore banks within the historic range of the stoneworts. As many ditches are now cleared on a regular cycle, it seems that, provided the water quality is maintained at a suitable level, the future of many of our stoneworts is looking a lot better.

The UK Biodiversity Action Plan for this species is available at UK BAP.


This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:


Lives or grows for just one year.
Slightly salty water.
Microscopic particles involved in both dispersal and reproduction. They comprise a single or group of unspecialised cells and do not contain an embryo, as do seeds.
In animals, the spiral or convolutions in the shell of a snail. In plants, a set of leaves, flowers, or branches that spring from a stem at the same point and encircle it.



Image credit

Great tassel stonewort in water  
Great tassel stonewort in water

© R. V. Lansdown

Richard Lansdown


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