Ecological Flora of the Central Chilterns

Transcription

1 Ecological Flora of the Central Chilterns Section 31: Convolvulaceae, Solanaceae Henbane Tony F Marshall, M.A. (Cantab.) March 2017

2 Family Convolvulaceae Bindweeds 31.1 Field bindweed Convolvulus arvensis Common native perennial throughout our area, in arable land, rough ground, and established grassland of all sorts. Druce (1926) said it was "abundant" and a "garden pest". While the plant can be difficult to eradicate (it has very long tap-toots, up to 5m or so!), it does not these days generally present a real nuisance, preferring lighter soils to our clays and perhaps having declined in abundance (as has been documented nationally - Hill et al 2004). Identification Long stems prostrate on the ground or twining anticlockwise around other plants, with arrow-shaped leaves and trumpet flowers, pure white or more or less striped pink. Notable sites Common beside the fields of Hampden Bottom Farm and in allotments, and in Little Stocking Meadow, but only really absent from our woodlands, where it only occurs in very open glades if at all. Ecological associates With two known British galls (in our region) and only two leaf-miners (one rare and not recorded from Bucks), this plant does not seem to have attracted many predators. No galls or leafmines have been recorded locally. A couple of Longitarsus leaf-beetles are known to specialise in feeding on bindweeds, but only one L. rubiginosus has been recorded locally, and that not since 1922! There are, however, two common moth species whose caterpillars eat bindweed - White plume moth Pterophorus pentadactyla and another plume moth Emmelina monodactyla, as well as the much less common Four-spotted moth. The two plume moths are commonly found in houses and are obviously supported by the persistence of field bindweed in gardens and allotments. The flowers are scented and provide nectar for a wide variety of insects that effect cross-pollination, but the seeds seldom mature in our climate (the plant is better adapted to warmer climes). While a seed-bank can build up gradually, the main means of propagation is vegetative. Human associations This plant has inevitably drawn the attention of gardeners, and not in a complimentary way, as the smallest piece can root and regenerate. It has therefore garnered a variety of vernacular names - "withywind", devil's guts" and "bellwine/bellbine" are noted for our area, and "bethwine" around Hambledon and Marlow (Trevor Hussey, pers.comm.), referring variously to its winding and binding stems (withe is an old word for willow), bell-shaped flowers, or persistence. ("Beth" seems to represent a convergence of "bell" and "withe".) The roots are known as a purgative, while the plant's ability to extract heavy metals from soil, while making it mildly toxic, also makes it useful for cleaning agricultural land that has been excessively treated with chemicals. It is also capable of fixing nitrogen (like the clovers) and is useful to the gardener in enhancing the fertility of soils, so it may be best to work with the plant rather than against it, merely curbing its excesses in colonisation. Derivation The names really say it all; even the Latin name refers to its twining properties and field habitat. Varieties Plants with broader and narrower leaves have been designated as varieties, and there is a marked difference between the extremes, but the distinction does not seem to be systematic and is not recognised in Stace (2010). Whether or not it has pink stripes and the intensity of them has attracted some study, but again this seems to have been inconclusive. Field bindweed Field bindweed with very well-marked flowers Hedge bindweed

3 Hedge bindweed Calystegia sepium 31.2 Native perennial scattered in hedges throughout our area, but not really common. Identification Like a large version of field bindweed, with bell-flowers twice the size, 3-6cm, and always white in our area. Notable sites It grows on the boundaries of all our local allotments and on roadsides, eg in the hedge along Green Lane, Prestwood. Ecological associates As for field bindweed; the large flower cups make good overnight shelters for insects. Human associations It is a spectacular vine and excellent cover for otherwise ugly fences (see the picture on p304 of Mabey, 1996, of such a fence in High Wycombe). Varieties Our plants are all ssp sepium. Large bindweed Calystegia silvatica Southern European species that is now well naturalised and almost as common as the similar hedge bindweed. Identification The flowers are even larger (up to 9cm), but the major difference is the calyx, the outer lobes (bracteoles) being much larger and expanded into a puffy pouch that totally obscures the inner calyx. Sometimes faint pink stripes can be seen on the outside of the petals. Notable sites Like hedge bindweed, this can be found on the boundaries of some allotments (Great Kingshill, Hazlemere, North Dean), by Sandwich Wood and along Bryants Bottom Road. Not recorded in Druce (1926). Varieties Var. quinquepartita with a split corolla sometimes escapes from gardens, although it has not been recorded in our area. Large bindweed Hairy bindweed Calystegia pulchra Only thrice recorded in our area, this is another casual introduction, probably a garden cultivar. It is like large bindweed but the flowers are pink or have pink stripes. The stalks are slightly hairy and winged beneath the flower. It has been recorded in the Hughenden area in 1998 and north of there at a later date, while I recorded it at Brickfields in 2001 (since disappeared). It is a more recent introduction, not featured in Druce Calystegia silvatica var. quinquepartita

4 Dodder Cuscuta epithymum 31.3 This parasite mainly on gorse but also on heather was once locally abundant on the old heathy commons and mentioned by Druce (1926) for the Kingshill area, but he also adds "less common since World War I". It is now extinct and I know of no site currently in the Chilterns, now that the heaths are largely gone, gorse much less common and heather rare. Thin red stems trail untidily, sometimes thickly, over the host plant, bearing spherical clusters of small pink flowers, leaves reduced to scales. The name first appeared after Anglo-Saxon times in Middle English as doder; the name in German is dotter, which also means "yolk", but what the connection might be is quite unclear. Greater dodder Cuscuta europaea Another native parasite, this one trailing over riverside plants, usually nettles. It has never really been a Chiltern plant: Druce (1926) says "local, rare, sporadic" referring to an 1867 record for Hughenden (the latest for our area). More recently it used to grow along the banks of the Thames and the Ouse. I have searched almost the whole of the previous known sites along the Thames in the last couple of years but have not found it at all. It does, however, still grow by a small stream tributary to the Ouse close to the University campus in Milton Keynes. The flower clusters are more conspicuous than those of the smaller Dodder ("diddy dodder"?), but the host plants and habitat are sufficient to tell them apart anyway. Dodder on gorse Greater dodder on stinging nettle

5 Family Solanaceae Nightshades 31.4 The nightshades are a dramatic family of generally very poisonous plants (although they ironically include some of our major foodplants like potato and tomato). The flowers are generally very showy, as if advertising "touch me if you dare". The fruits are fleshy berries. Bittersweet (Woody nightshade) Solanum dulcamara This is a common native perennial of bushy places and rough, especially damp, ground. Identification This flower has the archetypal Solanum look, narrow purple petals becoming down-turned, surrounding a protruding column of yellow stamens. They grow in clusters on the trailing stems that are only weakly climbing and have simple leaves, often, especially lower leaves, with two lobes at the base. The flowers are followed by berries that are bright red when ripe. Notable sites The bare edges of ponds are a good place to search - it occurs at the Sheepwash, the ponds at Honor End, Big Park, Cherry Tree Farm, Andlows Farm and Lodge Wood. But it grows in all sorts of other places too, like the built-up areas of Prestwood, Collings Hanger Farm, Boug's Meadow, beside Hampden Road, Great Missenden Station and in hedgerows. Galls Two galls are known in Britain but not recorded locally. Mines About four leaf-miners have been recorded on Solanum in our part of Britain, of which two are found locally - the micro-moths Scrobipalpa costella and Acrolepia autumnitella. Other ecological associates The leaves are often found full of "shot-holes" caused by the Potato Flea-beetle Psylliodes affinis. The Bittersweet Flea-beetle P. dulcamarae might also be expected and could have similar effects, but it has not yet been recorded locally. Another flea-beetle, the Downy Potato Flea-beetle Epitrix pubescens also occurs in the general region and might be expected to be present. More work needs to be done on these small beetles locally. Human associations This is one of the less poisonous members of the family, and its woody stems can be chewed as a mild narcotic. Its juice mixed with lard was used as an ointment for chilblains. From the plant's point of view the toxic chemicals are a protection from attack from most insects. Derivation Although the berries are undoubtedly poisonous, they are so bitter that anyone trying them would quickly spit them out. The aftertaste, it is said, is sweet, hence the name. "Nightshade" comes from its two component syllables, and similar constructions are used in both German and Dutch, but why these plants have this name is not certain. It has been argued that it is because they grow in the shade and flower at night, but neither are particularly relevant features. Others say it refers to their narcotic effect or use (in the case of the more toxic plants) as poisons, and the allusion of the name aptly reflects their air of mystery and threat, the progeny of darkness and the underworld. Bittersweet with unripe berries

6 31.5 Mine of Acrolepia autumnitella on bittersweet Black nightshade Solanum nigrum Native annual of arable land and disturbed places generally, not common in our area, but scattered fairly widely (although not recorded from the eastern parts, from Great Missenden to Cobblershill). It was not mentioned for our area in Druce (1926). Identification Low, sparsely hairy, plant with patent white petals around the column of yellow stamens, leaves that may be toothed, and berries that are black when ripe. Notable sites As an annual it is sporadic in its occurrence. Latest records are from Peterley Manor Farm (2016), Great Hampden churchyard, Studridge Lane Pond, and the field north of Gomms Wood (2015), Lodge Lane in Prestwood and under maize in a field above Longrove Plantation (2013). In Mabey (1996) there is a record of plants growing unusually large and bushy in greenhouses near Chesham, reported by Peter Casselden. Galls None known. Mines As for bittersweet. Other ecological associates See bittersweet. Human associations This plant seems to have occasioned little notice. Varieties Our plant is ssp. nigrum. A conspicuously glandular-hairy subspecies schultesii, introduced from the Mediterranean, occurs very commonly as a casual in London and might be expected to appear in more urban areas of the Chilterns such as High Wycombe or Amersham. Black nightshade subspecies nigrum Black nightshade subspecies schultesii

7 Potato Solanum tuberosum 31.6 This plant was introduced from South America as a crop several centuries ago and has now become a staple food. It often persists from overlooked tubers remaining in the ground or from thrown-out potatoes on rubbish heaps. Identification The leaves are pinnate, the flowers either white like Black nightshade or purple like Bittersweet, but larger than either, the berry green or purplish. Notable sites Casual and therefore unlikely to recur at the same sites for very long. There are two records for our area - beside the track along the top of Denner Hill in 1997 (from throw-outs with other vegetables) and at Cryers Hills Cemetery in Galls Four galls are known to occur on potato tubers, the results of nematodes and diseases. Although none of these are recorded locally, it is likely that some do occur among cultivated crops. Mines Some of the miners on Solanum above likely occur on potato plants, although we have no specific records of them. Other ecological associates The Potato Capsid bug Closterotomus norwegicus is very common and feeds on a wide variety of plants, of which the potato is one. Bob Fastner of Prestwood reared fruit-flies from pupae he found inside the fruit of a potato plant in his garden. These were identified by Martin Harvey as Drosophila immigrans, first found in this country in 1921, probably from Asia, though nowadays it is more or less cosmopolitan. It probably feeds on any ripe fruit. Human associations As an important foodcrop, the potato has been subject to much commercial research and experiment leading to a great range of varieties of tubers, although it seems to make little difference to the plant above ground. Although the tuber is generally edible, green ones are poisonous, as are the berries, although the latter are not allowed to develop on crops and will only occur on wild escapes. Derivation "Potato" is an adaptation of the native Haitian term for sweet potato, batata, although this is an unrelated species. As the sweet potato was "discovered" by European explorers first, the name was transferred to the similar-looking tubers of the true potato.

8 Tomato Solanum lycopersicum 31.7 This is another plant from South America that has became a staple of European cooking. Although it may occur less as a survival of a field crop or a throw-out than then potato, its seeds survive the human digestion system and are passed through sewage, frequently germinating around sewage plants. Identification With pinnate leaves like potato, but yellow flowers, the familiar green to bright red fruit, and roughly bristly hairs. The whole plant when handled has a very characteristic pungent smell, given off by alkaloids in its leaves to ward off insect attack. Notable sites Twice recorded in Hughenden Valley and also on the Lovell Estate in Prestwood as an escape, but not persisting. Galls Three galls are recorded, two of them only on the roots. None recorded locally. Mines Two leaf-miners have been documented on tomato in Britain. One of these Chromatomyia horticola is present locally on a wide variety of plants. Other ecological associates The photograph (which was taken in Reading) includes the effects of Tomato leaf mould Passalora fulva and Early blight Alternaria solani on its leaves. Both are common diseases of tomato plants and no doubt occur in our area too. Human associations An important food-crop for its fruit which, unusually for this family, are edible. There is disagreement over whether the leaves are poisonous, but they would probably be harmful if eaten in quantity. Derivation From the Aztec word tomatl, a staple ingredient in Mexican cuisine. The Incas also knew the plant but regarded it merely as a weed!

9 Deadly nightshade Atropa belladonna 31.8 Rare native perennial of chalk scrub or shady waste places, imposing in both flower and fruit. Identification Large bushy plant with simple leaves and glandular hairs giving off an unpleasant odour. The flowers occur singly, each on a stalk from the base of a leaf. The flowers are shortly tubular with five spreading lobes that are purple-brown and somewhat sinister in appearance. The large black berries that follow are set within five enlarged spreading calyx lobes forming a conspicuous corona. Notable sites While a perennial, this plant is of sporadic appearance and does not always survive long, perhaps needing soil disturbance to expose the seed-bank - it was reportedly widespread after the great storm of 1987 uprooted many beeches. There have only been three records - Hampdenleaf Wood in 1994, Flagmore Wood just north of Hughenden Manor in 1999 (reported by the prominent coleopterist A.P. Foster) and Doctors Meadow, Little Missenden in 2001 (Marcus Olozulu). The latter is an unexpected record away from the chalk, the site being on alluvial soil. With no more recent records (and it is certainly no longer at the third site), this plant may well be extinct in our area. It is, however, present nearby at Pulpit Hill, and elsewhere in the Chilterns at Ellesborough Warren, Watlington Hill, Cliveden, Dancers End Reserve and the southern section of Wendover Woods. Druce (1926) states "local Hughenden", so the Flagmore Wood site may be of long standing. Ecological associates No galls known, but the two possible leaf-miners recorded in this country are both present locally - Chromatomyia horticola and Acrolepia autumnitella. The Flagmore Wood site was reported by A.P. Foster in the course of recording the Belladonna Leafbettle Epitrix atropae, a Notable B species restricted to this plant. Human associations This species is well-named - it is packed with the alkaloid hyoscyamine which will cause death, especially in children, if eaten in more than minimal quantity (three berries are said to be enough). Folk medicine used the less virulent woody nightshade (above) in preference to this plant, which was seen as too dangerous (Allen & Hatfield 2004), although poisoners would have found it useful. In small doses this substance causes dilation of the pupils and quickening heartbeat (for both of which it is still used medicinally), drying of the mouth, and stomach cramps. Its use as a beauty aid in enlarging the pupils is the origin of the specific name bella donna "beautiful lady".

10 Henbane Hyoscyamus niger 31.9 This plant is just as deadly as the last species and contains the same alkaloid toxin, hyoscyamine, which takes its name from this plant. It occurs on disturbed ground on chalk but, being annual, is very unpredictable. Identification This is also a bushy plant, long-haired, its leaves simple or with a few large lobes. The flowers are clustered on short stalks in two rows along upper shoots that elongate in fruit. They are creamy with purple-brown veins and deep purple throat. Although quite different from deadly nightshade, it looks just as sinister. Notable sites Only once recorded in our area in 1987 by Alan Showler at Hughenden Valley Primary School (!!!). I presume it was not allowed to survive long. It was not recorded by Druce (1926) for our area. Ecological associates No galls and one miner have been found on henbane in this country; the miner has not been found locally. (The scarcity of insect associates on this and the preceding plant are a testimony to the effectiveness of its poisonous juices.) Epitrix atropae (see above) may occur and also the Henbane Leaf-beetle Psylliodes hyoscyami (although it has not been recorded locally). Human associations The plant had folk uses as a hallucinogen and painkiller, as well as a poison whose use, like deadly nightshade, goes back to classical Roman times. It was famously used by Dr Crippen in more recent times. Derivation "Bane" is a poison; the plant is quite likely to appear beside hen-runs because of the soil disturbance (I have myself seen it in just such a situation), so it may well have occasioned a few fowl deaths in former times. Note how seeds have been caught in the long hairs Dead plant with seed-capsules Close-up of seed-capsules

11 Thorn-apple Datura stramonium This common American plant (there known as Jimsonweed, from Jamestown, Virginia) occurs casually here from time to time in waste places, usually these days from bird-seed. The long white trumpet flowers are unmistakable and so are the spiny brown seed-pods. It occurred in a garden in Cherry Close, Prestwood, in Like most of this family it is very toxic unless used in a controlled way medicinally. Japanese-lantern Physalis alkekengi Sometimes found surviving briefly close to gardens. It has white flowers and a bright red-orange inflated seed-case covering a small red berry. It is cultivated for its dried fruiting stems as a table decoration. Found in Bryants Bottom in 2004.

12 Wild tobacco Nicotiana rustica Sticky-hairy annual introduced from America for tobacco crops, but now just occurring casually as an escape from gardens where it is grown for its long narrow yellow-green trumpets that attract longtongued moths at night for its nectar. It was found in Great Missenden in 1997 by Roy Maycock Red tobacco Nicotiana forgetiana Like the last but with leaves clasping stem and red flowers. Found besides the Chequers pub, Prestwood, in Hybrid tobacco Nicotiana x sanderae Garden cultivar, a hybrid between the last and N. alata, which is white flowered. The hybrid is intermediate in its characters. Found 2010 at Nanfan Farm by Val Marshall. Red tobacco [Teaplant Lycium spp. Commonly grown as hedging and persisting in many places. Not recorded in our area, but can be found, for instance, alongside the main road approaching West Wycombe from High Wycombe. Two species are established - L. barbarum (Duke of Argyll's teaplant) and L. chinense (Chinese teaplant): both originate from China. The former is much the most likely to be found; it was first introduced to Britain in the 1730s by the then Duke of Argyll.] Hybrid tobacco Duke of Argyll's teaplant