The Wey and Arun Canal

Latest sightings
Frogbit and Bladderwort in flower. Photo: Richard Bullock

Source: Abraham, Frances. “The Wey and Arun Canal.” Sussex Botanical Recording Society Newsletter, no. 91 (November 2020). https://www.sussexflora.org.uk/wp-content/uploads/2022/02/Newsletter_nov_20.pdf.

In August Nick received an intriguing email from the Surrey botanist Richard Bullock. Richard and his wife had been walking part of the towpath which borders a restored section of the Wey and Arun Canal near Loxwood. They had found a Bladderwort in flower which they did not identify to species but suspected to be Utricularia australis. There was also Hydrocharis morsus-ranae (Frogbit). Neither is shown in that area in The Flora of Sussex (2018). The only native site known for U. australis in West Sussex is Amberley Wild Brooks, but it has not been seen there for some years.

I shot off to Loxwood and in no time was admiring hundreds, possibly thousands, of flowering spikes of U. australis. The flower shape of a fresh specimen distinguishes it from U. vulgaris (Greater Bladderwort), confirmed by the differing distribution of glands within the spur. I find the latter character excruciating but not quite impossible to investigate. There were quantities of Frogbit. Westwards from Loxwood, both species occur sporadically from the village right into Ifold, sometimes in abundance. East of the village, there are gaps along heavily shaded stretches but elsewhere they extend to Drungewick Lane. I had no high hopes of the easternmost length of the Canal from Drungewick Lane to Drungewick Lock as it has been largely drained for repairs this year. However, where a little open water remained, there they both were again. Altogether three tetrads have been added to the Sussex distribution: TQ03F, TQ03K and TQ03Q.

Other open water species included Potamogeton natans (Broad-leaved Pondweed), Nuphar lutea (Yellow Water-lily), Spirodela polyrhiza (Greater Duckweed) and Persicaria amphibia (Amphibious Bistort). Except in the most shaded parts, the margins and banks were colourful with Lythrum salicaria (Purple Loosestrife), Lysimachia vulgaris (Yellow Loosestrife), Stachys palustris (Marsh Woundwort), tousled heads of Scirpus sylvaticus (Wood Club-rush) and much more.

The submerged leaves of Bladderwort. Photo: Richard Bullock

A few years ago I saw the eastern stretch from a narrowboat with Mary Briggs. Her sight had almost gone but she was keen to hear what plants were visible, and delighted that Rorippa amphibia (Great Yellow-cress) was frequent. I couldn’t find it this time but in general I see from my old notebooks that the flora of the Canal has not changed greatly since I first visited in the 1990s.

The apparently sudden arrival of these two distinctive species in such great quantity is curious. Richard speculates that the lack of canal traffic in this strange year may have something to do with it. The canal is certainly quieter than normal and the vegetation more luxuriant. There was no boat traffic except for occasional kayakers peacefully paddling. Utricularia is a sporadic flowerer and could have been overlooked, although the submerged leaves are clearly visible from the towpath. The Flora shows no Hydrocharis in the hectad to the south either, but this year I have seen it in numerous places both elsewhere in the Canal and in the R. Arun in TQ02L, TQ02S and TQ02T. Of course nowadays one must bear in mind that many people think that they are doing a good deed if they introduce any old species native to the UK into areas of countryside where they may or may not occur naturally.

Introduction does not seem likely here, but we will probably never have a certain answer to the riddle. Whatever, this is a delightful walk, filled with interest. Just keep one eye on the plants and the other on the path as you pick your way through the dog mess.

Bladderwort flowers with the leaves of Frogbit. Photo: Richard Bullock