Category Archives: Rivers

Two scarce riverbank plants

Earlier this month, I took a walk along the River Avon from Conham to Hanham. to check out some of the scarce plants which occur locally in riverbank habitats. The highlight was this Greater Dodder (Cuscuta europaea), a parasite of the Common Nettle (Urtica dioica): the upright green stems are those of the nettle, and the red stems twining around them belong to the dodder.

This is a nationally scarce plant, found in only a handful of areas in southern and central  England. Locally, it occurs in two areas. It is found along the River Avon from Bristol upstream to Bath, and again to the east of Bath into western parts of Wiltshire; its other stronghold is along the River Severn (mainly around Gloucester but with an outlying site near Frampton-on-Severn).

 Dodder

The closely-related Common Dodder (Cuscuta epithymum) also occurs in our area, and is also a scarce plant, despite its name. It is found in heathland and dry grassland and parasitises among other things, species of gorse, heather and thyme. It has smaller flowers, although to be certain of the identity of a dodder specimen, a flower has to be dissected under a microscope, to look at tiny features such as the shape of the minute scales at the base of the inner surface of the flower and the relative length of the sex organs.

Here’s the area where I found the plant photographed above:

Also present in good numbers throughout this section of the Avon was Small Teasel (Dipsacus pilosus), the scarce relative of the ubiquitous Common Teasel (Dipsacus fullonum). In and around Bristol, it is found on the River Avon between Bristol to Bath, on the River Frome in northeast Bristol, on the River Chew, and scattered other localities, often in or on the edge of woodland.

Small Teasel 1 Small Teasel 2
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Beautiful Demoiselles

Vic Savery sent me these excellent photos of Beautiful Demoiselle (Calopteryx virgo), which he took at Three Brooks Nature Reserve in Bradley Stoke yesterday. Demoiselles are our largest damselflies, and one of our most noticable and easily-recognised, and like the Common Clubtail I featured in an earlier post, mainly river-dwelling species.

 female demoiselle1  beautiful demoiselle1
Beautiful Demoiselle, 14 June 2013, Bradley Stoke, Bristol, Vic Savery (naturenutz.net)

There are two species of demoiselle in Britain; Banded Demoiselle (Calopteryx splendens), the other species, has a narrow dark patch across the wings in males, with extensive clear areas at both the base and tip, and has a blue rather then blue-green abdomen. Female Bandeds are more similar in appearance to female Beautiful Demoiselle, but with green-tinged rather than brown wings. There are other species of demoiselle in continental Europe, including the Copper Demoiselle (Calopteryx haemorrhoidalis) with a copper-red abdomen.

Beautiful Demoiselle prefers faster-flowing streams with stony riverbeds, whereas Banded likes slower-flowing muddier-bottomed rivers; however the two are often found together, indicating some overlap in the types of river they prefer. Ther British distributions differ: Beautiful Demoiselle is mainly found in Wales, southern and western England, with an outpost in western Scotland, whereas Banded Demoiselle is found throughout England and Wales but only just makes it into southern Scotland.

Around Bristol, both species are found on many of our rivers and streams, including the Avon, Chew, Cam, Wellow, Yeo, and both the Bristol and Bath River Fromes. They are also often found away from rivers (e.g. around ditches on the North Somerset levels, or at ponds and lakes throughout the region).