London: East End Canals

5 September 2014

This trip was almost entirely a replica of the walk for the Botanical Society of the British Isles (BSBI) led by John Swindells on 11 September 2014, ten years ago to the week.  Given that many of the plants in such an urban location are adventives, we felt it would be interesting to see how many could be replicated and what newcomers there might be.

          We began from Mile End tube station, walking north up Grove Road on the east side.  A small concrete wasteland behind railings immediately yielded Annual Mercury Mercurialis annua (a common weed in London), Bilbao's Fleabane Conyza floribunda (which has become almost as common as Guernsey Fleabane Conyza sumatrensis these days), Greater Celandine Chelidonium majus, London Rocket Sisymbrium irio (nowadays rather difficult to find), Red Valerian Valeriana dioica and Buddleia Buddleja davidii, the latter occurring throughout the walk, as it did ten years before. 

Annual mercury

 When we reached the terraced houses we were pleased (and rather surprised) to find that Pink-headed Knotweed Persicaria capitata was still growing in the small concrete front garden of no.36.  Our inspection of this plant brought some unwanted attention from a lady searching the waste-bins along this street, perhaps thinking we had discovered some useful treasure before she could obtain it.  She is probably still mystified by our interest in this plant!  It was presumably a garden escape originally, but has certainly succeeded in becoming well-established, even if it shows no signs of spreading beyond this one site.

Pink-headed Knotweed, Grove Road

 Across the road, at the north end of Mile End Park is a small allotment, the unkempt surrounds of which provided a number of interesting plants.  Chicory Cichorium intybus, Black Horehound Ballota nigra, Bristly Ox-tongue Picris echioides, Fat Hen Chenopodium album, Fennel Foeniculum vulgare and Lucerne Medicago sativa were all recorded ten years ago.  Others not mentioned in the summary of that walk (www.bsbi.org.uk/FieldMeetings2004.pdf) were: Feverfew Tanacetum parthenium, Argentinian vervain Verbena bonariensis (an increasingly common escape, perhaps because it is offered by all the garden centres), Apple- and Pepper-Mints Mentha x villosa & x piperata, and what we assumed at the time to be a Small Teasel Dipsacus pilosus in seed, but on second thoughts may actually have been an escaped Yellow-flowered Teasel D. strigosus, as the native pilosus seems unlikely here.

Lucerne in seed

We continued south through Mile End Park, where there was plenty of rough grassland and more lucerne, fennel and bristly ox-tongue.  Also still here from ten years ago were Hoary Mustard Hirschfeldia incana, Mugwort Artemisia vulgaris and Wild Carrot Daucus carota, plus the hairy form of Black Nightshade Solanum nigrum ssp schultesii (not seen until later in the walk last time) with its commoner subspecies nigrum.  Seeding with meadow flowers in the last decade may have explained the addition now of Greater Knapweed Centaurea scabiosa, Hedgerow cranesbill Geranium pyrenaicum, Lady's Bedstraw Galium verum, and Red Bartsia Odontites verna, but the large stands of Hemlock Conium maculatum were more likely natural colonisation.  There was also Fairy-ring Champignon Marasmius oreades.

Mile End Park

Solanum nigrum schultesii

 Crossing this grassland we reached the banks of the first canal, the Grand Union, which we followed south to its end.  The edge of the canal itself had Gypsywort Lycopus europaeus, Skullcap Scutellaria galericulata, and Beggarticks Bidens frondosa, all of which had been recorded ten years before.  There was also Narrow-leaved Michaelmas-daisy Aster lanceolatus.  On the opposite side were the large leaves of Water Dock Rumex hydrolapathum. 

Common skullcap

Narrow-leaved Michaelmas-daisy

 By the side of the path there were also, as before, Guernsey Fleabane Conyza sumatrensis, lots of Perennial Wall-rocket Diplotaxis tenuifolia, Pellitory-by-the-wall Parietaria judaica and the schultesii form of Black Nightshade.  Other plants here included the Burnet-saxifrage Pimpinella saxifraga, Hoary Plantain Plantago media and Bladder Campion Silene vuylgaris, more familiar in limestone grasslands, plus Pink-sorrel Oxalis articulata and Shaggy Soldier Galinsoga quadriradiata. 

Perennial wall-rocket

 At the base of a tree was a group of Poplar Fieldcap fungi Agrocybe cylindracea, while a conspicuous caddis-fly Mystacides longicornis (with long-antennae, looking more like a longhorn moth) was found resting on canal-side vegetation.

Poplar fieldcap

Mystacides longicornis

 On the earlier trip a strip of long-grass parkland, near where Ben Jonson Road crossed the canal, had yielded a number of plants, but the character of this had changed, there being signs that meadow-flower seed had been applied, with Viper's Bugloss Echium vulgare, Cornflower Centaurea cyanus (seen in 2004 only in Mile End Park), Goat's-rue Galega officinalis, and Musk Mallow Malva moschata now present.  Shaggy inkcaps Coprinus comatus grew here.

Cornflower

Musk mallow

Grand Union Canal & typical ruderal plant habitat.  "R.I.P. Troy Davis" refers to a black person executed in 2011 in Georgia for murder of a policeman, although he always claimed he was innocent and evidence emerged after his sentence that another person had committed the crime.

This isolated chimney beside the Grand Union is apparently just a sewage ventilation shaft

South from here all the way to Limehouse Basin had been very productive in 2004, with 13 further plants being recorded, but the sides of the canal and the tow-path had clearly been tidied up since then and plants were sparse.  Only three of these plants were seen again - Fat Hen, more Black Nightshade ssp schultesii, and Narrow-leaved Ragwort Senecio inaequidens. 

Narrow-leaved ragwort

The paving around the upmarket residences around Limehouse Basin itself had also been rigorously cleaned of plant life and the Prostrate Spurge Euphorbia prostrata that had got a hold here was now gone.  We did, however, see Water Bent Polypogon viridis, present in 2004 a little further along the route.  It was the only plant that seemed to be able to survive the pavement cleaners.

Sterile environment of the Limehouse Basin

From the Basin we followed the Limehouse Cut canal north.  There was abundant Pellitory-by-the-wall on the walls as before, and also Mexican-tea Dysphania (formerly Chenopodium) ambrosioides, Water Bent, and Tall Nightshade Solanum chenopodioides were still present as well.  Both the Mexican-tea and the Tall Nightshade managed to grow from the canal-side brickwork itself.  This stretch had much more vegetation than by the Grand Union and we also recorded the cultivated form of Red Clover Trifolium pratense, Mexican fleabane Erigeron karvinskianus, Water Figwort Scrophularia aquatica, Hemp-agrimony Eupatorium cannabinum, Hemlock Water-dropwort Oenanthe crocata, Tomato Solanum lycopersicum, Dwarf Mallow Malva neglecta, Garden Pansy Viola x wittrockiana, Purple Toadflax Linaria purpurea, Trailing Bellflower Campanula poscharskyana, Round-leaved Cranesbill Geranium rotundifolium, and the wall ferns Black Spleenwort Asplenium adiantum-nigrum, Hart's-tongue A. scolopendrium and Common Polypody Polypodium vulgare.  This made up in quantity, if not in quality, for the plants missing from alongside the Grand Union compared to 2004.

Limehouse Cut

Tall nightshade

Tall nightshade, showing woody stem

Mexican tea

The Limehouse Cut ends at its junction with the Lea Navigation at Bow Locks.  It was here in 2004 that we were able to see together and compare all three Bur-marigolds Bidens spp.  Unfortunately the locks were at this time under reconstruction and there was no access to the area successfully botanised previously, although we could see plenty of plants of Bidens just past here, north along the Lea Navigation.  Near Bow Locks, we were still able to record Fat Duckweed Lemna gibba, as before, but saw no sign of the Water Fern Azolla filiculoides that had previously grown with it.  We also saw Marsh Woundwort Stachys palustris (recorded a little later last time) and Orange Balsam Impatiens capensis, not noted in 2004.  The bur-marigolds gave us a lot of trouble, as all the plants were vegetatively very similar.  London Bur-marigold Bidens connata is supposed to have leaves predominantly less lobed than in Trifid Bur-marigold Bidens tripartita, and Beggarticks should have had more leaves with extra lobes, but all plants were like the normal form of tripartita, although when we examined seeds from various plants beside the Lea Navigation, we found representatives of all three species, as determined by the direction of barbs on them.  It appeared to us that the three species had been subjected to considerable hybridisation that had made them difficult or impossible to tell apart on characters other than the seeds themselves.

London bur-marigold (according to the seeds)

Along the Lea Navigation we not only saw the Fennel, Celery-leaved Buttercup Ranunculus sceleratus, Rigid Hornwort Ceratophyllum demersum, and Large-flowered Waterweed Egeria densa that had been recorded before (although we saw no sign of Danewort Sambucus ebulus or Floating Pennywort Hydrocotyle ranunculoides), but we added many more species to our list, much more Mexican-tea, Perennial Wall-rocket, Shaggy Soldier and Goat's-rue, but also Hop Humulus lupulus, Ivy-leaved Toadflax Cymbalaria muralis, Smooth Sumac Rhus glabra, Gallant Soldier Galinsoga parviflora, Oxford Ragwort Senecio squalidus, Wild Mignonette Reseda lutea, Bouncing Bett Saponaria officinalis flore pleno, Common Evening-primrose Oenothera biennis, Pale Corydalis Pseudofumaria alba, Greater Duckweed Spirodela polyrhiza, South American Waterweed Elodea callitrichoides, and Nuttall's Waterweed E. nuttallii.

Pale corydalis

Three waterweeds - from left: large-flowered, Nuttall's & South American

We stopped off at House Mill Café at Three Mills for a drink and snack.  Beyond here we were close to the Olympic Stadium at Stratford that had been built since 2004 and was now being rebuilt for alternative uses, making the walk rather noisy.  The Anish Kapoor "Orbit" structure was clearly visible.  This towpath was probably on the circuit for tourists in 2012 and it was marked by a huge amount of street art, much of it very impressive.

Oympic stadium under reconstruction & "Orbit"

Lea Navigation & mural by the street artist "Sweet Toof"

Exotic wildlife by the Lea Navigation

Mural on the White Building by the street artist "Ekta Ekta"

At Carpenters Road we turned on to the towpath west along the Hertford Union Canal.  There was more street art along here, compensating for a lack of new plants for a while, but we eventually came across a few small plants of Common Amaranth Amaranthus retroflexus, seen at the same spot ten years ago - we were very surprised to see this usually ephemeral plant again.  We knew it had been near the classic site for the rare Tapegrass Vallisneria spiralis (TQ3602983396, 100m before Grove Road), and we were pleased to see its long strands floating just beneath the surface of the water well out into the canal.  A few strands were near enough for us to check its identity (as there were no flowers).  Also along this part of the canal we saw our third Conyza Canadian Fleabane C. canadensis (the fourth, Argentine C. bonariensis, continues to elude us), Russian Vine Fallopia baldschuanica, Orange Mullein Verbascum phlomoides, Garden Lobelia Lobelia erinus, and, finally, on the balustrade of Grove Road Bridge, Henbit Lamium amplexicaule.  We did not see London Rocket at Bow Wharf as in 2004, but we had already seen it at the beginning of our walk.

Tip of tape-grass frond showing characteristic small teeth at apex only

Beggarticks (as identified from seeds) by Hertford Union

Orange mullein

Garden lobelia by Hertford Union

Henbit on Grove Road Bridge

Mural, Hertford Union Canal

Mural by "Ali Hamish", Hertford Union Canal

Unusual bronze sculpture as street art, by "Jonesey", beside Hertford Union Canal

Hertford Union Canal near the tape-grass site

At Grove Road we walked south to the Ecology Park near Roman Road.  In 2004 we had seen Fringed Water-lily Nymphoides peltata and Lesser Bulrush Typha angustifolia here and both were still evident, the latter quite abundant.  The park had, however, got far more overgrown in the last ten years and there was no sign of Buttonweed Cotula coronopifolia or American Galingale Cyperus eragrostis anymore.  We did see more Celery-leaved Buttercup and a patch of Stone Parsley Sison amomum, and, less pleasingly, plenty of New Zealand Pygmyweed Crassula helmsii.  We also saw Emperor Dragonflies and were able to watch a Brown Rat scuttling around a pond edge and even doing a little swimming. 

Roman Road Ecology Park

Lesser bulrush

We crossed to the nearby towpath of the Grand Union Canal to take this north-west to Bethnal Green (this was not part of the 2004 route).  The canal here was full of moored barges and plants were very scarce, but we did see more Common Amaranth and Rigid Hornwort, plus one final new addition - Common Millet Panicum miliaceum.

Common amaranth

Common millet

We finally turned south down Cambridge Heath Road towards Bethnal Green tube-station, stopping for an evening meal at the excellent restaurant (Corner Room) in the old Town Hall, now a hotel.