10-July London’s July Wildflowers

Both these loosestrifes can be found at Langham lake, Runnymede, along with water forget-me-not Myosotis scorpiodies, arrowhead Sagittaria sagittifolia, frogbit Hydrocharis morsus-ranae and an interesting collection of aquatic umbellifers, including the highly poisonous hemlock water dropwort Oenanthe crocata. Its leaves can easily be confused with celery, although they are darker, firmer and more shiny. The bigger problem in the past was that its roots look like parsnips. Some of its leaves added to a cheese sandwich have resulted in death within three hours.

Its close relations are rarer e.g. fine-leaved dropwort O. aquatica which can be found in north east London, river water dropwort O.fluviatilis, sulphurwort O. silaifolia and tubular water dropwort O. fistulosa all of which can also be found in the Runnymede area as well as the wet meadows around Chertsey. Most water dropworts are poisonous although not as virulent as hemlock water dropwort so even though they may smell of parsley they are all best left untouched.

may catch your eye this month are figworts, bur marigolds, balsams, skullcaps, water mints and water lilies as well as greater spearwort, marsh pennyroyal, marsh ragwort and marsh woundwort. Less noticeable are the pearlworts, bedstraws, docks, persicarias and plantains. Looking into or on the surface of water, Canadian pondweed, hornwort, water milfoil and various Potamegetons and duckweeds may also be seen.

The balsams are a particularly attractive group. It is the Himalayan balsam Impatiens glandulifera that gets the most attention. This is mainly because it is an alien which aggressively takes over some riverbanks to the exclusion of everything else and also partly because of its fruits. When fully ripe, these dramatically explode when touched. Orange balsam I. capensis is one of our few orange flowers. It can be found along some portions of the river Lea.

Skullcap Scutellaria galericulata has unusual blue-violet flowers arranged in tight pairs along its stems. This is usually encountered by itself at the edges of canals or even on the walls bordering the Thames. Its cousin lesser skullcap S. minor is much more likely to be found in marshy areas. Water figwort is capable of reaching a staggering two and a half metres in height and was so well thought of by early gardeners that both variegated and white-flowered forms were sold as garden plants. Water lilies are probably the favourite aquatic plant for most Londoners. Both our native white water lily Nymphaea alba and yellow water lily Nuphar lutea can now be seen in flower in Crane Park Nature reserve. Most of the water lilies we see are planted and occasionally they hybridise. The fringed water lily Nymphoides peltata is much rarer but can still be seen on Longwater at Hampton Court.

Other rarer wild water plants to look out for this month are meadow rue Thalictrum flavum, marsh pennywort Hydrocotyle vulgaris, water soldier Stratiotes aloides, water purslane Lythrum portula and the truly inconspicuous chaffweed Anagallis minima. Water soldier is very unusual as it spends most of its life submerged on the surface of mud with its serrated spear-like leaves pointing upwards. However, in July it dramatically releases itself from the mud and floats to the surface to show off its flowers, each of which has three large white petals. Alas this is all to no avail as in this country they never set seed before they descend again to the muddy depths in August.

Chaffweed is very easily missed as it is only a few centimetres high and has tiny pink or white flowers just one or two millimetres in width. It may still occur on Reigate heath on bare wet woodland paths. Two other rarities: various-leaved starwort Callitriche platycarpa and water whorl grass Catabrosa aquatica can both be seen along the Basingstoke canal. Marestail, although a flowering plant, usually gets mistaken for a horsetail. In July it sends up above the water surface a flower of sorts. The flowers are the smallest imaginable, lacking any petals or sepals to talk of.

Being wind pollinated, petals are not needed. Other truly minute flowers this month are produced by the duckweeds and the smallest of all our native flowering plants Wolfia arrhiza. This aquatic is so small it generally gets missed, even by plant recorders.

The showiest of our waterside plants are probably the monkey flowers Mimulus spp. There are three in London, mainly seen in water gardens. Occasionally, they do occur in the wild, especially along parts of the rivers Colne and Derwent. The monkey flower M. guttatus is the most likely to be seen with its custard yellow flowers, Blood-drop emlets M. luteus is more attractive on account of the red splashes on its yellow flowers.

Last and the most strange is the musk plant M. moschatus. This was once a great garden favourite but the plant mysteriously lost its musk scent across the whole world in 1912.

A pleasant and easy way to become acquainted with waterside plants this month is just to walk along the banks of the River Wandle as it meanders through Beddington Park and then Morden Hall Park. Including any ponds and nearby marsh you can find up to seventy different species of waterside and submerged plants in both places. These include five different water cresses (Rorippa spp.), three different duckweeds, stonewort, monkey flower, brooklime and royal fern in Beddington Park and five different sedges, two bur-reeds, water fern and skunk cabbage in Morden Hall Park.

July is also the best month to visit one of the rarest of London’s semi-aquatic habitats, bogs. It is here where our small number of insectivorous plants can be found. Surprisingly on Wimbledon Common for the time being both Sundew Drosera rotundifolia and Butterwort Pinguicula vulgaris can still be found, although they may well have been re-introduced. Sundew has reddish leaves bordered with hairs that end in tiny glistening sticky drops. When an insect comes to investigate it soon finds itself trapped and as it struggles both the hairs and leaves bend to secure it more firmly.

This can all happen in less than ten seconds. Then unseen digestive juices are secreted which break down the insects’ softer parts so that its vital nitrogen can be absorbed. When the leaf re-opens you can often see insect legs or wingcases left that have been reluctant to break down. These get blown away by the wind.

Butterwort employs a similar strategy but in this case there are no hairs on its fleshy leaves. However, they are sticky and roll up to engulf any insect that lands on them. Epsom forest is still a place to look for both these plants as well as one of the most unusual of all insectivorous plants, Bladderwort Utricularia vulgaris. Its small, canary yellow flowers set on thin stems coming out of water are the first thing you notice. These give no clue to what is happening below the water surface. There is a mass of floating filaments with small, clear bladders attached to them.

If the whole plant is temporarily put in an aquarium with some waterfleas it is not long before the waterfleas swim too close and are suddenly sucked into a bladder and entrapped. Unlike our other insectivorous plants Bladderwort does not dispose of its prey with digestive juices but just keeps them entrapped till they die of starvation and then, at their leisure, they absorb their nutrients.

One of the most atmospheric bog habitats to visit is on Keston Common. This is where Charles Darwin is believed to have studied the plants before writing his book on the subject. Although any insectivorous plants may now be hard to find other attractive bog plants such as Bog Asphodel and Cotton grass may still be seen. Among the seven sphagnum mosses recorded there are the brightly coloured red species Sphagnum capillifolium ssp. Rubellum and S. magellanicum.

On Chobham common there may also be a chance of seeing another insectivorous plant Sarracenia purpurea, the Pitcher plant. It is vase-shaped and usually half full of water in which the insects drown. It is an alien from America and much more likely to be seen in garden centres.

Woodland Flowers

Woodland paths often have their own distinct plant communities. This month silverweed, centuary, St John’s wort and figwort all stand out. The figwort most frequently seen is common figwort Scrophularia nodosa usually along the edges of damp paths. Its small, strangely shaped, deep burgundy flowers stand out on tall stems. When present, it can be an indicator that the rest of the wood is species rich. The similar looking water figwort S. auriculata is also common and not always found beside water.

There are two others worth searching for. The green figwort S. umbrosa is, unfortunately, very rare. It has leaves more deeply and sharply toothed than the common figwort. The yellow figwort S. vernalis, which has yellow flowers and bright green leaves, is a little easier to find as it is naturalised at Kew. In the seventeenth century, Gerard tells us it grew “in moist meadows from London to Hornsey” and there was also a white form which is now unknown. In France, figworts are called ‘siege herbs’ on account of them being eaten during the siege of La Rochelle in the seventeenth century. They must have been a famine food of last resort, as the tubers have such an unpleasant smell.

One or two garden plants also turn up in woodlands at this time of year e.g. Tutsan Hypericun androsaemum, Rose of Sharon H. calcinum, various Oxalis spp and an alien golden rod Solidago canadensis. Our own native golden rod S. virgaurea is unfortunately rare and rapidly disappearing. It prefers rocky areas in open woods where it usually chooses to grow singly. It has been replaced partially by S. canadensis which was imported from north America as a garden border plant. It seeded so easily and was so invasive it was quickly thrown out. Either way, it soon formed the dense clumps we see around London today. It also has a relative S. gigantea, which is not quite so invasive, but is also on the move.

Other attractive species that get noticed at this time of year are Burnet saxifrage Pimpinella saxifraga, Water avens Geum rivale, Betony Stachys offinalis, and one or two bellflowers Campanula spp.

Two impressive ones are Canterbury bell C. latifolia and the Nettle-leaved bellflower C. trachelium. The first can still be seen in some woods in the far north of London and the second is still common enough at the edges of chalky woods on the North Downs. Common gromwell Lithospermum officinale, with its seeds like miniature pointed pearls, is found in similar situations.