Ecological Flora of theCentral Chilterns

Section 20: Elaeagnaceae, Rhamnaceae,Cannabaceae, Urticaceae, Cucurbitaceae,

Celastraceae

Pellitory-of-the-wall growing on Grenfell vault, Taplow House

Tony F Marshall, M.A. (Cantab.)August 2014

20.1Family ElaeagnaceaeSpreading oleaster Elaeagnus umbellataGarden shrub of Asian origin often planted along roadsides and occasionally occurring bird-sown in the wild.Lanceolate green leaves silvery when young; sprays of small tubular scented creamy-yellow flowers (formed of foursepals only - there are no petals) are succeeded by red berries in autumn. It occurred as a relic of cultivation onthe site of former allotments in Great Kingshill in 1996, but was destroyed when the site was cleared and sown tograss. Its relative Hippophae rhamnoides (Sea buckthorn) is a rare native on the east coast but also widelyplanted in roadside schemes, and as such likely to occur in the Chilterns. It has very narrow silver-grey leaves andorange berries.

Sea-buckthorn (as a native in Norfolk)

Family Rhamnaceae (Buckthorns) 20.2(Purging) Buckthorn Rhamnus catharticaNative shrub scattered in our area in hedges and scrubon chalk, but never very numerous.Identification A few spines usually occur on the twigs.Simple oval leaves have impressed veins and finelytoothed margins. Small greenish-yellow flowers withfour petals occur in clusters, followed by purplish-blackberries.Notable sites In chalk scrub at Prestwood Picnic Site,Longdown Bank and Little Stocking Meadow; in theedges of Widnell, Hampdenleaf and MeadsgardenWoods; in hedges in the upper parts of fields onHampden Bottom Farm and along Kingstreet Lane.Galls Four known in Britain, two recorded locally on theleaves of buckthorn: the mite Aequsomatus annulatusand the aphid Trichochermes walkeri.Mines Again four known in Britain, of which two havebeen noted in our area: the micromoths Stigmellacatharticella and Bucculatrix frangutella.Other ecological associates The buckthorn isecologically renowned as the food-plant of theBrimstone butterfly - the sparse occurrence of theshrub compares oddly to the prevalence of thebutterfly, although no other food-plant has yet beenidentified. It only lays its eggs on the young shoots, sothat regular cutting of hedges prevents buckthornbeing used by brimstones. The caterpillars of the DarkUmber moth also feed on buckthorn. The crown rustPuccinia coronata regularly occurs on our buckthorns, aswell as on its other host, grasses. Pollinated by variousflying insects.Human associations The berries (and bark) arepoisonous, acting as an immediate laxative (hence thename "purging").Derivation In medieval Latin the name was cervi spina"stag's horn", translated into early English as "buck'shorn". This may refer entirely to the stout spines, orthe prefix may merely connote a common shrubregularly browsed by wild deer.Varieties Its fellow native, Alder buckthorn Frangulaalnus, only grows on wet acid soil and can be found inpeaty valley bottoms south of the Chilterns, often withalder. The leaves lack serrations.

Under-leaf with brown patches of crown rust and greyish patches invein angles where Aequsomatus annulatus are feeding

Leaf-mines: left, Bucculatrix frangutella,; right, Stigmellacatharticella

Family Cannabaceae (Hemp family) 20.3Hop Humulus lupulusNative perennial vine to be found scrambling over hedges in a small number of scattered places.Identification The fruits ("hops") are familiar as constituents for brewing beers - the vines are often seen asdecoration in pubs (eg Royal Standard of England, Forty Green) and unmistakable. The palmately-lobed leaves arevery rough. Flowers occur on separate plants as either small greenish-yellow male catkins or tight female clusters.The latter develop into the familiar leafy cones.Notable sites Along Rignall Road, at the back of the car park opposite The Harrow pub, along the main road inLittle Missenden, and a field hedge just west of Naphill (Trevor Hussey). It is much more frequent below theChilterns in scrub alongside the River Thames.Galls One known, caused by a downy mildew not recorded in our area.Mines Of three possible, we have recorded one locally, the fly Agromyza flaviceps.Other ecological associates A mildew Podosphaera macularis is common on the leaves. The caterpillars ofButtoned Snout moth feed on hops, as do those of the Comma butterfly, which was observed breeding on hop inher own garden in Prestwood by Christine Hoskins.Human associations The fruit lend the distinctive bitter flavour to beer (distinguishing it traditionally from "ale"not brewed with hops, although the terminology is now muddied), this flavour coming from "lupulin", a mixture ofoils exuded by the fruit that makes one comatose - "hop pillows" have been used for helping people sleep. They(rather than the alcohol) explain the warm restful feeling experienced by beer-drinkers. Hops were famouslycultivated in Kent for the brewing trade. Folk medicine has long used the sedative properties of hop.Derivation The Old English term for hop was hymele, from a Germanic root also contained in the genus nameHumulus, which was monkish, not Roman, Latin. By the 15thC this was replaced by hoppe from a Dutch word, andwith different Germanic root (hoppo in Old Saxon). The specific Latin name lupulus meant "little wolf", also usedto refer to a snagging thorn, referring to the rough leaves.Varieties The narcotic properties of Hop become understandable when one realises that it is a member of thesame family as Hemp Cannabis sativa. This can occur as an escape occasionally, although it tends to be destroyedas soon as people realise what it is - despite the fact that the plant cannot ripen sufficiently in the wild in thiscountry to develop the effective drug, so one might as well let it be. Our plant is generally ssp indica. A differentsubspecies (sativa) is cultivated for fibre, and this has too low a proportion of THC (tetrahydrocannabinol) formaking drugs.

Hops

Leaf-mine of Agromyza flaviceps

Family Urticaceae (Nettles) 20.4Common (or stinging) nettle Urtica dioicaThis is one our most ubiquitous, iniquitous and common plants, and one that is increasing as soils becomeincreasingly nitrogenous (nutrified) with continuing air and water pollution. As a native, however, it has acquired animportant ecological role in supporting a wide range of wildlife and possibly supports greater diversity than anyother herbaceous plant. In Davis (1991) it is stated that 31 insects are restricted to nettle and a further 76 arestrongly associated with it.Identification Touch and see! (A quick firm grasp of a leaf between the fingers, however, crushes the poisonoushairs and prevents one being stung.) Stinging hairs are abundant on the leaves and stems. The flowers are smalland green, hanging in dense catkins, male and female on different plants ("dioecious", hence the specific name).Notable sites A site would be notable if it did not include nettle. Unfortunately I do not know of one. Patches ofnettle are most vigorous and extensive on enriched soil - around dung-heaps, in neglected horse-pasture, wheregarden rubbish has been dumped, around rabbit burrows, across deserted habitations, in hedges around fertilisedfields, and so on. After many years Prestwood Nature is still battling nettles at its Boug's Meadow reserve, whichhad been used as horse pasture before restoration. Nettle is one of the few herbs to be sufficiently common andnotable to be incorporated into place-names - eg Nettlebed in Oxfordshire. Its persistence and spread is assistedby the variety of means it has for doing so - seeding, underground rhizomes from the roots, similar above-groundstolons that take root at the tips, prostrate or trampled stems rooting in contact with soil, and broken-offfragments, carried by man or other mammals, also capable of regenerating.Galls Six known in Britain, and three locally common: the dramatic orange distortions caused by the rust Pucciniaurticata, leaf-curl caused by the psyllid bug Trioza urticae, and swellings caused by the fly Dasineura urticae.Mines Three leaf-miners are known in Britain, all flies of the genus Agromyza. The mines of all three are commonin our area: A. anthracina, A. pseudoreptans and A. reptans.Other ecological associates A patch of nettles can harbour a seething mass of wildlife. With high uptake ofnitrogen and phosphorus compounds and minerals and the manufacture of sugars and vitamins, the plants provide arich food source. Their ability to spread into large patches by means of deep underground runners also providesshelter, and further protection by the deterrent effect of the stinging hairs. From the insect's point of view,nettles are manna. Take a sweep-net to a patch and a single swing will gather dozens of different species,especially plant-bugs such as Nettle ground-bug Heterogaster urticae, Brassica bug Eurydema oleracea (I saw ahuge mating swarm of them on nettles beside Hampden Road in May 2007), Green shieldbug Palomena prasina(which may lay their eggs on the underside of the leaves), Scolopstethus affinis, Plagiognathus arbustorum,Heterotoma planicornis, Liocoris tripustulatus, Grypocoris stysi, Deraeocoris flavilinea, Orthonotus rufifrons;planthoppers - especially Eupteryx urticae; aphids - most commonly theCommon nettle aphid Microlophium carnosum; weevils like Apionurticarum, Ceutorhynchus pollinarius, Nedyus quadrimaculatus, Phyllobiuspomaceus and P. pyri; pollen beetles Brachypterus glaber and B. urticae;earwigs; thrips; and snails. Ladybirds, the ground beetle Demetriasatricapillus; rove-beetles, and many spiders and harvestmen like Mitopusmorio regularly occur as predators on other insects. Larvae may includethose of the fly Ceroxys urticae, the nymphalid butterflies Red admiral,Small tortoiseshell, Peacock and Comma; and the moths Nettle-tapAnthophila fabriciana, Small magpie, Mother-of-pearl, Setaceous Hebrewcharacter, Mottled rustic, Burnished brass, Plain golden Y, Silver Y, TheSpectacle, Dark spectacle and Snout. (Altogether 27 moth species feedwholly or mainly on nettle.) This abundant insect life attracts tits andother small birds, hedgehogs, shrews and amphibians, while finches andtheir allies enjoy the plentiful seeds. Apart from Puccinia urticata rustabove, fungi commonly found on nettles are Puccinia iridis, Nettle rashLeptosphaeria acuta and Crepidotus luteolus (the last two on deadstems). There is even another plant parasitic on nettle - Greater dodderCuscuta europaea, although this does not occur in our area, formerlybeing common along the banks of the Thames, but now rare, although itcan be seen at Milton Keynes near the university campus. One may saythat all these species are common - but they are common because theirmain resource is ubiquitous. The frequency with which "nettle" or such Nettle in flower

as "urticae" crop up in their names indicates that nettles are the primaryfood source for many of them. Going by the number of species makinguse of this plant, one could argue that the ideal habitat for biodiversityis a forest of ancient oaks with a ground layer of bramble (in open areasto encourage flowering) and patches of nettles. The fact that this mightnot be popular with humans is perhaps a bonus! On the other hand,nettles reduce the diversity of ground-plants because their densecolonies shade out other species.Human associations Apart from being a nuisance to bare-legged walkers(and this only reflects the plant's prevalence, itself indirectlyencouraged by human activities), nettles are actually as nutritious a foodresource to man as they are to invertebrates - the young tips have longbeen collected for making a healthy broth, or to make beer or tea(though note that in quantity they are diuretic). They also make a goodcompost. Like Hemp, nettles contain fibres that can be used to makethread, a use that goes back to prehistoric times, although nowadays anumber of tropical plants have proven to be more efficient for suchmanufacture. Even the stings can be used to positive effect, being foundto ease arthritis by applying nettles to the affected joints. (The hollowhairs act like a syringe to inject a cocktail of chemicals, includinghistamine, into our skin, causing pain and inflammation. For those withallergic reactions to nettle rash (urticaria) the only remedy is to takeanti-histamines. Contrary to old folk tales, dock leaves are of no use,though they appear to work by the cooling effect of pressing any freshjuicy leaf against the skin.)Derivation The linguistic root of "nettle" goes as deep as its physicalroots, being traceable as an "-nd-" stem back to ancient Greek a(n)dikeand early Indo-European languages, ultimately connected to the Sanskritdah "to burn". The Latin urtica similarly derives from Latin uri "to burn".Varieties Our plant is subspecies urtica. Ssp galeopsifolia is a stinglessvariety with narrower leaves found in very wet situations and notrecorded locally. If you think you have found it there is an easy way tomake sure.

20.5

Mines of Agromyza anthracina

Small infection of Puccinia urticata

Mines of Agromyza pseudoreptans and nymphs of the common nettle aphid

20.6

Small tortoiseshell on nettles

Red admiral on nettle in seed

7-spot ladybirds mating on nettle leaf. The fuzzy white styles showthe flowers at top to be female ones. The males have yellow pollen.

Comma on nettles

Small tortoiseshell caterpillar on nettle

Young small tortoiseshell caterpillars feed communally in webs

20.7Small nettle Urtica urensAlthough Urtica urens shares the stinging hairs ofdioica, it is a much smaller plant and an annual ofcultivated or disturbed ground, not forming persistentpatches.Identification Apart from size and habitat, small nettleis easily spotted from the shorter, roundish leaves. Theflowers are of mixed gender on each plant.Notable sites Despite being a frequent arable weedacross the Chilterns, we have only ever had three localrecords. It grows commonly on Peterley Manor Farm,but apart from that we just have a single record fromAbbey Park in 2007 and a vague one from "Prestwood" in1952 (which might relate to Peterley Manor Farm). Itgenerally prefers light soils, but Peterley Manor Farm ison clay.Ecological associates These do not seem to have beenrecorded separately from Urtica dioica. It probablyshares a few of the stinging nettle's associates, but itcertainly does not support anything like such a widecommunity.

Mind-your-own-business Soleirolia soleiroliiMediterranean plant introduced into gardens, but often spreading beyond and becoming naturalised in bare places,especially walls and in damp shady spots.Identification This is a prostrate plant with small round leaves on wiry reddish stems. The flowers are non-ostentatious, tiny, red, at the base of the leaf-stalks.Notable sites There are four recorded sites. The simplest to find is at the base of the wall at the east end ofHoly Trinity church, Prestwood. It is also at the base of walls in Great Missenden High Street, and recorded fromgardens in Perks Lane and Hughenden Valley.Ecological associates None known.Human associations Imported as a ground-cover plant for gardens, especially old cottage gardens. Another nameis "Mother of thousands" because of its ability to spread (although this seems vegetative rather than by seed), butthis name is also applied to some other unrelated plants; also "Baby's-tears" from the small leaves.Derivation Probably from the undemonstrative way in which it spreads untended, often overlooked.

Mind-your-own-business

Pellitory-of-the-wall Parietaria judaica 20.8This is a native perennial which also has a predilection for the base of walls, quite commonly growing along streetsin old Chiltern villages and towns.Identification Simple lanceolate leaves are alternate up red stems, which trail or grow erect. Flowers green, tiny,in loose clusters, red from the calyces, at the base of each upper leaf.Notable sites Recorded in 1984 from the walls of Great Missenden parish church, but no longer there since theywere cleaned.Ecological associates No galls and just one miner (only in SW England) are known in Britain.Human associations Used in herbal medicine as a diuretic, a property shared with others of the Urticaceae.Derivation While "nettle" is derived from an ancient word for "burn" (see above), it is interesting that, for quite adifferent reason, "pellitory" drives from the Greek for "fire" - pur. This was used in the Greek puretos "fever"and gave the name to the plant "feverfew" purethron used as a cure for fever. This was incorporated in the Latinpyrethrum used for various herbal plants (and surviving today in the plant-name Pyrethrum) and thereby came intoOld French as peletre, from there into English as pellitory. "Pellitory-of-the-wall" therefore means "the herb thatgrows by walls".

Pellitory-of-the-wall

Family Cucurbitaceae (Gourd family) 20.9White bryony Bryonia dioicaHedgerow scrambler often confused with the unrelated (and quite dissimilar) black bryony (see section 12.3);fairly frequent on chalk in our area, but not as common as black bryony.Identification Vine with tendrils opposite the leaves, which are palmately lobed, pale green and matt. Smallgreenish flowers are followed by poisonous berries that are deep red and also matt, not shining like black bryony.Notable sites Prestwood Picnic Site, Longdown Bank, Dillwyn Plantation, around Hughenden allotments and playing-field, Kingstreet Lane and the main road into Little Missenden.Galls Buds may be affected by two species of Jaapiella (gall-midges), but neither has been found in our area.Mines One known in this country, the common polyphagous fly Chromatomyia horticola. Although not recordedspecifically on white bryony, it is highly likely that its mines would occur if sought.Other ecological associates Pollinated by bees and other insects. The southern European Bryony ladybirdHenosepilachna argus was first reported in this country in 1997 and is spreading. It has not so far been recordedin our area but might well be found. A recent 11-spot ladybird record from a hedge by Hampden Road could havebeen this species (which also has 11 spots, though in a slightly different pattern) and this needs following up.Human associations The whole plant is toxic, especially the tuberous roots. Although there are some vaguereferences to its use in folk medicine, this would seem to have been unlikely and certainly dangerous. A dozenberries would kill a grown man, a tuber would kill a cow.Derivation "Bryony" is directly derived from the ancient Greek word connected with bruein 'to swell', referring tothe swollen roots common to this family. "White" is from the pale matt appearance compared to Black bryony.

Muscid fly on white bryony

Marrow Cucurbita pepoMarrows and other garden gourds (including courgettes, a variety of the same species) can sometimes occur for ashort while, probably as part of garden rubbish. I saw Marrow at Brickfields in 1995 and Courgette on Denner Hillin 1997, but there have been no other records.

Family Celastraceae (Spindle) 20.10Spindle Euonymus europaeusNative hedgerow shrub that is quite frequent on the chalk, increasingly so because its attractiveness has led to itsinclusion in most modern mixes for replanting hedges.Identification Unmissable in autumn with its leaves turning bright red and unique four-lobed pink fruits thatbreak open to reveal the four orange seeds inside. The leaves are simple long oval and the flowers inconspicuousgreenish-white sprays, although the green four-sided twigs usually pick it out.Notable sites Prestwood Picnic Site, hedges on chalk on Hampden Bottom Farm, Bryants Bottom Road, Boss Lane;lots in newly planted hedge east of Andlows Farm.Galls Three are reported on the leaves in Britain, two occurring locally: the mites Cecidophyes psilonotus andStenacis convolvens.Mines Oddly, no leaf-miners are reported in Britain on spindle.Other ecological associates Often infected by the scale insect Unaspis euonymi. Caterpillars of four moths inour area feed on spindle - Scorched carpet, Ypsolopha mucronella, Yponomeuta plumbella and Spindle ermineYponomeuta cagnagella. The last two both feed within webs and can form major infestations that defoliatebushes. Three such infestations were seen in 2006, cagnagella along Perks Lane (George Lewis) and HampdenBottom Road (myself), and plumbella at Cryers Hill (Martin Albertini).Human associations The hard wood of young branches found uses in the past for small tools like skewers, pegs andspindles (hence the name). The leaves and bark are purgative, but the main folk use seems to have been in theform of a powder made from these for rubbing on the heads of children to rid them of lice.

Spindle flowers and leaf-margins galled by Stenacis convolvens Autumn leaves & fruit, Prestwood Picnic Site

Spindle berries showing orange seeds

20.11Family MoraceaeFig Ficus caricaThis Asian import, cultivated for its fruit, has become naturalised in warmer areas of the country, mainly inLondon, where it is quite common. It has not been seen in the wild in our area, but one planted specimen hassurvived well in the garden of a house at the east end of Perks Lane. It bears fruit which sometimes ripen.