#46 Flowering Rush by Ray Goulder
Meet Ray Goulder, former lecturer in freshwater ecology at Hull University!
Ray taught freshwater ecology at Hull University from 1972 to 2009, whilst undertaking research in aquatic microbial ecology, and later developed his interest in learning and teaching―especially field work. Since retiring he has partaken in extensive voluntary work for the Canal & River Trust and has spent many enjoyable days walking the towing paths of canals in Yorkshire, and adjacent counties, recording aquatic plants, and thinking about how plants in canals interact with the ways in which canals are used, managed, and enjoyed. Currently he is studying Wolds village ponds―this combining his interest in plants and local history. Ray can be contacted at: r.goulder@kategoulder.karoo.co.uk
Figure 1. The flowering head and erect stem of Flowering Rush in the margin of the Pocklington Canal at East Cottingwith in August 2020.
Ray’s chosen species is the Flowering Rush Butomus umbellatus. Flowering Rush is the only member of the family Butomaceae and is distinctive amongst ‘rush’ and ‘reed’-like wetland and aquatic plants in having colourful, conspicuous, and attractive flowers. It is native to Yorkshire and is found in nutrient rich canals, rivers, and drains―good places to see it include the River Derwent, the River Hull, the Pocklington Canal, the Leeds & Liverpool Canal, and many other similar canal environments. Flowering Rush blooms around July-September (see right, Figure 1). Its flowers stand out amongst the preponderant green shades of reeds and rushes at the margins of waterways - the petals are pink and are carried in umbels at the end of long unbranched stalks. The flowering stalks can be up to about 1.5m tall and usually overtop the surrounding linear, rush-like leaves. These are triangular in cross section and often have a twist to them. The plant is part of Britain’s native freshwater flora, is represented over many thousands of years in the pollen record, and in North and East Yorkshire is likely to have been part of the flora of the formerly extensive, now largely lost, wetlands of the Humberhead Levels, Holderness, and the Derwent Valley. To Ray, Flowering Rush is very much an axiophyte, that is a ‘worthy plant’ that a botanist will likely always be pleased to encounter. It is usually part of a diverse and conservation-worthy community of aquatic plants.
Flowering Rush was regarded by J F Robinson as a charismatic plant of East Yorkshire, to the extent that he chose it to illustrate the front cover of his 1902 Flora of the East Riding of Yorkshire. His flora describes the plant as very common, especially in drains in Holderness and along the River Derwent. The 2023 Plant Atlas 2020 emphasises the southern and eastern distribution of Flowering Rush in England, and it is encouraging to read that it remains frequent in its core range―although it is suggested that there may be decline in some areas. Today, in East and North Yorkshire, it thrives in the River Derwent and River Hull, and in the Pocklington Canal, where it can be seen from the towing path when not obscured by other tall marginal vegetation. Indeed, it tends to be found in canals throughout Yorkshire. In 2010-2016, Ray surveyed 223 lengths, extending over c.179km of canal. Flowering Rush was found in 30% of lengths and was the tenth most often recorded emergent aquatic plant―more information can be found in Ray’s 2019 book Canals, Plants and People: a Yorkshire Perspective. There is evidence that it may be extending its range in East Yorkshire; when Ray surveyed plants annually from 2003 to 2020 along the c.1.2km urban canal known as Beverley Beck, Flowering Rush was first found in 2014 and has since spread. The plant probably arose from propagules in top up water pumped from the River Hull. A good place to see the plant, while keeping one’s feet dry, is along the Leeds & Liverpool Canal in central Leeds. There is direct access to the towing path from the Granary Wharf exit of Leeds rail station. Walk westwards and many aquatic plants, including Flowering Rush, may be observed from the towing path.
A problem with recognising and recording Flowering Rush arises because, as with many water plants, its form is very variable, depending on variables such as water depth and current speed. When it is flowering it is easy to recognise. However, it often does not flower, and its leaves may be entirely submerged, trailing at the water surface, or emergent. They may be floppy or rigid and may vary greatly in size. Consequently, they can be difficult to distinguish from those of other ‘reed’ or ‘rush’-like plants―especially if they are out of reach. For this reason, it may be under recorded. Sometimes, loose fragments of leaves can be recovered, for example, from canals amongst accumulated plant debris behind lock gates. A key feature you can use to identify this plant, however, is that the leaves are an equilateral triangle in cross section. This is different from, for example, the leaves of Branched or Unbranched Bur-reed (Sparganium erectum and S. emersum) with which Flowering Rush is often found―in section their leaves are an isosceles triangle with one long side and two shorter equal sides. A further diagnostic feature of Flowering Rush (taken from R V Lansdown’s 2008 Field Guide to the Riverine Plants of Britain and Northern Ireland) is that if a leaf is snapped across, the separated parts remain joined by fine translucent threads.
Figure 2 (L). Flowering Rush, with floating leaves and without flowers, in the Leeds & Liverpool Canal in central Leeds. Perfoliate Pondweed (Potamogeton perfoliatus) and Fennel Pondweed (Stuckenia pectinata) are submerged in the foreground; June 2016. Figure 3 (R). Marginal vegetation in the Pocklington Canal at Storwood in July 2013; Reed Sweet-grass is in the foreground with Flowering Rush beyond, and the floating leaves and flowers of Yellow Water-lily in deeper water.
Flowering Rush sometimes grows unseen, in dense underwater beds of submerged leaves, as in the River Hull system in Frodingham Beck upstream of its confluence with West Beck. At other sites, as in the Leeds & Liverpool Canal in Leeds, the leaves may float at the water surface (see above, Figure 2). The plant flowers in shallow, marginal, water where the leaves are rigid and erect. These flowering plants tend not to form pure stands, but instead are often found with a variety of other emergent species (see above, Figure 3). For example, in the Pocklington Canal, this diversity was apparent in July 2020, when along about 1.1km of waterway, between Walbut Lock and Thornton Lock, Flowering Rush was frequent in the margins and was accompanied by Reed Sweet-grass (Glyceria maxima), Branched Bur-reed, and Common Reed (Phragmites australis), which were dominant or abundant, and also by, less abundant, Bulrush (Typha latifolia), Reed Canary-grass (Phalaris arundinacea), Yellow Iris (Iris pseudacorus), and Amphibious Bistort (Persicaria amphibia). Along this canal, Flowering Rush tended to grow in slightly deeper water, along the outside of the emergent marginal vegetation, beyond which were the floating leaves of Yellow Water-lily (Nuphar lutea). Boat trips run by the Pocklington Canal Amenity Society (https://www.pocklingtoncanalsociety.org/boat-trips) provide an opportunity to get close to water plants in this canal.
Recording and monitoring
Recording of Flowering Rush, as with many other aquatic plants, can be set around with problems. It grows in mud and/or water, sometimes deep, and so is often not easily accessible. It can readily be recognized if there are flowers, otherwise recognition on the basis of the often-unreachable leaves requires a degree of familiarity with the plant - binoculars can help. Better ecological information is obtained if the entirety of the marginal emergent plant community is recorded. Recording this community in quadrats is usually unfeasible and/or hazardous but bankside recording along defined lengths of waterway is usually possible for those interested in recording aquatic plants.
Further information and acknowledgements
NEYEDC would like to thank Ray for his time and expertise in helping to create this blog.