London: Thames from Kew to Richmond

29 August 2014

This walk was mainly along the tow-path by south bank of the Thames from Kew to Richmond Lock and back along the north bank, which was partially waterside and partially through streets.  We were right under the flight-path from Heathrow and the conversation-drowning brain-pummelling roar of aeroplanes every few minutes was wearing all day, even blotting out the screams of the Ring-necked Parakeets so well established in this area.

View of Thames from Richmond Lock, with tow-path to Kew to the right

After buying pastries for lunch from a market stall by Kew Gardens tube-station, we started off with a spin around Kew Gardens.  We were too early for the autumn colours of the trees and although the planted borders were very colourful, many outdoor flowers were finished.  The rampant Spreading Yellow-Sorrel Oxalis corniculata gave some brightness to rockeries and bark-mulched soil, where toadstools like ink-caps and Shaggy Parasol Macrolepiota rhacodes ssp bohemica were already beginning to appear.  A few Meadow Saffrons were variously standing or collapsing in the grass.

Spreading yellow-sorrel

Meadow saffron

At any time of the year there are always some trees worth a look.  Near the Palm House we noticed the globular brown fruits of an Asian Pear Pyrus pyrifolia, but resisted sampling them, although supposed to taste like pear and be very juicy.  They are speckled with white lenticels like Sorbus fruits.

Asian pear

In the Mediterranean Garden by King William's Temple two trees stood out for their distinctive bark - Cork Oak Quercus suber with its soft thick cracked variegated bark now unfortunately going out of fashion for corking bottles, and the Cyprus Strawberry-tree Arbutus andrachne with striking red bark peeling in strips.

Cork oak

Cyprus strawberry-tree

Nearby we could not help noticing several Paper Mulberry trees Broussonetia papyrifera, with their attractive globular orange flower-heads and elegant leaves.  The fruit is edible (it is a member of the mulberry family) and the bark was used for paper-making in ancient China.  It is, however, an invasive plant in some tropical areas.

Paper mulberry flowers and leaves

Just west of the Princess of Wales Conservatory is a famous old Ginkgo Ginkgo biloba ("Heritage Tree") with its long pendent branches of leaves descending like a shower, planted in 1762, when Britain declared war on Spain and Rousseau published his "Social Contract".

Old ginkgo bole and leaves

Nearby we stopped to celebrate the birthday of the 200-year-old Corsican Pine planted in 1814, the year when the most famous Corsican, Napoleon Bonaparte, was exiled to Elba.

200-year-old Corsican pine

There is usually some artwork celebrating the world of plants at Kew - on our spring walk here we encountered giant wooden mushrooms.  This time it was trees clothed in knitting patterns and some incongruous sheep.

Leaving by the Elizabeth Gate we walked through Kew Green to the Thames tow-path, walking west, to see if any of the exotics recorded for this stretch of the river remained.  These plants tend to be ephemeral, however, and we did not see the California Brome or the Ball Buddleia we had seen many years ago, nor Fig or Tree-of-heaven, but there were still some plants of interest, despite the vegetation being regularly cut and generally pretty dull.  One speciality of the Thames we were to find, but not until much later.

          Walls had Harts-tongue Asplenium scolopendrium, Black Spleenwort A. adiantum-nigrum, Wall-rue A. ruta-muraria, Polypody Polypodium vulgare, Ivy-leaved Toadflax Cymbalaria muralis, Pellitory-by-the-wall Parietaria judaica, and the lichen Cladonia humilis.

Cladonia humilis

Waterside plants were mainly Gypsywort Lycopus europaeus, Purple Loosestrife Lythrum salicaria, Pendulous Sedge Carex pendula, Wild Angelica Angelica sylvestris, and Water Figwort Scrophularia aquatica, along with some aliens: lots of Indian Balsam Impatiens balsamifera, Orange Balsam I. capensis, and occasional Garden Angelica Angelica archangelica with its thick-winged seeds and greenish, rather than pinkish, flowers.  Common blue damselflies Enallagma cyathigerum were active.

Male common blue damselfly

Wild angelica

Orange and Indian balsams

At this time of the year we are inevitably drawn to the fleabanes.  We identified Canadian Conyza canadensis. Bilbao's C. floribunda and Guernsey C. sumatrensis, but did not see any of the Argentinian with its red-tipped bracts.  Other flowers of the rough grass were Greater Celandine Chelidonium majus, Hedgerow Cranesbill Geranium pyrenaicum, Green Alkanet Pentaglottis sempervivum, Bristly Ox-tongue Picris echioides, Travellers’ Joy Clematis vitalba, Lesser Burdock Arctium minus, Horse-radish Armoracia rusticana, Black Horehound Ballota nigra, Oxford Ragwort Senecio squalidus and Prickly Lettuce Lactuca serriola.  Some of the lesser burdock exhibited an unusual condition of phyllanthy, a proliferation of leaves below the flower-heads - we were not sure whether this was the result of an attack by some virus or just a mechanical response to being severely cut back: the plants in question were all low and close to the ground.  The result was attractive and worthy of becoming a garden cultivar!

Lesser burdock with a proliferation of leaves below the flower-heads

Many of the plants grew on the precipitous stone rampart descending to the river, including many of the fleabanes and clumps of Michaelmas-daisy.  Where we could sample the latter they turned out to be Narrow-leaved Aster lanceolatus.

Narrow-leaved Michaelmas-daisy

Trees along the way included Grey Alder Alnus incana, Turkey Oak Quercus cerrifolia, Hybrid Oak Quercus x rosacea (with mines of the moth Stigmella roborella) and Hybrid Black Poplar Populus x canadensis (which had the distinctive spiral petiole galls of the aphid Pemphigus spyrothecae and the leaf galls caused by the fungus Taphrina populina).

Grey alder

Hybrid oak

Spiral gall on stalk of hybrid black poplar leaf

There were also several fruit-bearing trees of the rarely-seen Black Walnut Juglans nigra, which has more leaflets than the common species, these leaflets being well-toothed.  The bark is streaked sooty-brown and looks very dark from a distance, like Corsican pine.

Black walnut with green fruit

Just before we reached Richmond Lock there was a solitary plant of Perennial Cornflower Centaurea montana, an increasing garden escape.

Perennial cornflower

Crossing the bridge at the lock, on the other side we immediately came across our first Galinsoga, both species at once, not only lots of Shaggy-soldier G. quadriradiata, with its long white hairs, but also one plant of Gallant-soldier G. parviflora, sometimes referred to as "Kew weed".  Being close to its relative, the smaller flowers and the shorter, less dense stem-hairs were very apparent.  It was ironic that we had to cross the river out of Kew before we saw it.

Gallant-soldier

Shaggy-soldier

Although there is no tow-path this side of the river, we could walk beside it almost as far as Syon House.  Quite a lot of the plants were different on this side of the Thames, including Mind-your-own-business Soleirolia soleirolii, Annual Wall-rocket Diplotaxis muralis, Mexican Fleabane Erigeron karvinskianus, Annual Mercury Mercurialis annua, the miniature "palm-trees" of Common Liverwort Marchantia polymorpha and, draping the hedges, Hop Humulus lupulus, with leaf-mines of the fly Agromyza flaviceps and the moth, restricted to SE England, Cosmopterix zieglerella.

Hop

It was here that we saw one of the specialities of the day, on the stone embankment descending to the river, a plant of Thames Yellow-cress, the hybrid Rorippa x erythrocaulis between Marsh and Great Yellow-cresses, which has small petals longer than the sepals, longish lobed leaves with clasping auricles, and fruits on widely spread-out stalks.

Thames Yellow-cress

          Birds on the Thames mud-banks were mostly Cormorant, Black-headed and Great Black-backed Gulls, and Canada Goose.

          At Syon Park we had to divert from the river to pass by the House, whose gardens were unfortunately closed today for a massive Indian wedding, so we could not check out the old black mulberries planted there.  After this the path sometimes follows the river and at other times we had to walk through back streets and along busy main roads.  Other wasteland plants seen occasionally in this stretch were Lucerne Medicago sativa ssp sativa, Tansy Tanacetum vulgare, Sea Beet Beta vulgaris ssp maritima (still within the tidal reach?), Common Poppy Papaver rhoeas, Goat's-rue Galega officinalis, and Autumn Stonecrop Sedum 'Herbstfreude'.

A street hedge had Hybrid Hazel Corylus avellana x maxima.

          When we reached Kew Bridge Station we crossed the bridge back to the Kew Gardens side of the river again.  The road goes straight past Kew Church, our last destination for the day, for we had one more speciality to see.  The churchyard is not too tidily manicured, leaving plenty of rough grass and a chance for wild plants to survive.  Here we saw Meadow Saffron again, Bear's-breech Acanthus mollis, Peach-leaved Bellflower Campanula persicifolia, and, for the first time, Perennial Rocket Sisymbrium strictissimum with unlobed leaves, hairy underneath, a tall striking plant.  Unfortunately it had mostly flowered long ago and all but one plant were very dry and brown, but the one younger specimen still had green pods and was possible to photograph in front of a tombstone.

Perennial rocket in seed, Kew Churchyard

A short walk brought us back near Kew Gardens tube-station with time for a coffee before enjoying a meal at the Glasshouse Restaurant and reflecting on a day that was not perhaps botanically great but still had plenty of interest and two rare plants in Thames Yellow-cress and Perennial Rocket.