The Manual of Plant Grafting: Excerpt

8/10/2019 The Manual of Plant Grafting: Excerpt

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2 Usesof Grafting

ree rui and nu crops where i was he only easi-

ble mehod o vegeaive propagaion o mainainseleced clones. Tis uncion has remained isprincipal use in horiculure. Seleced culivars o

ornamenal rees are also geneically heerozygousand mus be propagaed vegeaively. Here againgrafing is used, perhaps because oher mehodso vegeaive propagaion are no successul or areoo slow or resul in poor roo sysems. Ornamen-al hardwood rees such as species o Fagus, Sor-bus, andBetulaare usually grafed as well as culi-

vars o needle-bearing (whorl-branched) conierssuch asAbiesandPinus. Fewer shrubs are grafed,alhough many choice shrubs like Hamamelisand

Wisteria are grafed as well as he ever-popularshrub roses.As developmens in rooing cutings under poly-

hene, mis, or og using base hea have developed,he use o grafing or many species has declined.he reason or his is ha cuing propagaion


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requires less skill and is less expensive han graf-ing. For example, large-flowered hybrid clemaisused o be propagaed by a nurse graf. In his ypeo graf, he scion is atached as low down as pos-sible o he roosock and only he op hal o he

scion is ied in, leaving a ail a he base. Te grafis poted so ha he scion and roosock are bohcovered wih he growing medium. In his way, heroosock suppors he scion unil he scion roosand can suppor isel. Rooing direcly rom sof-

wood cutings has now been successully devel-oped or hese plans and grafing is rarely used. Inoher species, he choice o propagaion mehodmay simply be he growers preerence.

Cutings and micropropagaion are now com-

monly used o propagae hybrid rhododendrons,as hese mehods are less expensive o carry ouhan graing and hey remove he problem oroosock suckering ha can occur wih Rhodo-dendron ponticumas he roosock. Grafed plans,however, will grow more quickly and usuallyflower sooner han hose produced rom cutings.

Acer palmatumculivars are anoher example oplans ha can be propagaed by cutings or graf-ing. While cutings, again, will be less expensive

han grafing, hey can be difficul o overwinerhe firs year. Sock plans are ofen orced inogrowh in greenhouses so ha cutings can berooed early enough o pu on growh beore mid-summer and o produce enough sores o energyo see hem hrough he winer. Grafed plans dono have his problem and will produce a largerplan more quickly han cutings will.

Alhough almos all oresr y ree species aregrown rom seed, superior selecions o species

(elie rees) are oen used o esablish seedorchards. Individual rees may show superiorcharacerisics suiable or imber producion,like rae o growh and sraighness o sem. Seedscould be colleced rom he paren and grown on,

bu grafing allows he seleced ree o be bulked

up quickly and is genoype mainained. Grafedplans will also produce seed much more quicklyhan seed-raised plans, as grafing shorens he

juvenile period in rees signiicanly. he inalbenefi is ha grafed plans produce seed lower

down he sem han seed-raised rees, and here-ore seed is easier o collec. For example, a heoresry saion o he Sofia Universiy o Foresry,Bulgaria, seleced rees o Pinus sylvestris(Scospine) are grafed o increase he number o supe-rior rees or seed producion. Te grafing alsomakes he ree maure more quickly and producecones lower down ha can be harvesed more eas-ily han a rom a seed-raised ree.

Te use o grafing, however, has been increas-

ingly used or a range o applicaions oher hanpropagaion. Tis means ha grafing will con-inue o be imporan even as echniques improvein oher mehods o propagaion. Oher reasonsor using grafing ollow.

To prevent pest damage

In he s, European grape vines (Vitis vinif-era), firs in England and hen spreading on o he

coninen, began o lose vigour and die. By ,wine producion in France had allen o . mil-lion hecolires rom . million hecolires jus years previously. Te plans were seen o havedamage o he roos ha gradually cu off he flowo nuriens and waer o he vine. Secondary un-gal diseases also occurred ha urher weakenedhe plans.

A firs, he cause o his damage could no beound. A microscopic yellow aphidlike insec was

ofen seen near damaged vines, bu i was no con-sidered a pes as i was never acually ound on heplans. Tree noed scieniss evenually ideni-fied he insec as he pes, and wo viiculurissound a soluion o he loss o yields in he French

vineyards.


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Phoenix, a variety of grape from Germany used to make white wine, growing in the demonstration

vineyard at the Royal Horticultural Society Gardens, Wisley. Phoenix scions have been

grafted onto SO4 rootstock. The plant has good resistance to phylloxera, has moderate

vigour, and tolerates lime-based soils, but does poorly under drought conditions.

Grafted Pinus sylvestrisat the Bulgarian University of Forestry outstation in Yundola, a

village in the coniferous forest belt, 1400 metres above sea level, between Rila and Rhodope

Mountain. Grafting scion-wood from selected trees not only increases the amount of seed

available quickly, but also produces it at a lower height making seed collection easier.


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French botanist Jules Emile Planchon is cred-ited with namingActinidia chinensis(kiwi ruit),

which was to become such an important ruitcrop in the twentieth century. He worked withPierre-Marie-Alexis Millardet, a French bota-

nist and mycologist, who is perhaps best knownor the development o the ungicide made romhydrated lime, copper sulphate, and water knownas Bordeaux mixture. Used by gardeners or many

years, this ungicide was finally withdrawn romuse in the United Kingdom in .

Planchon and Millardet eventually identifiedthe microscopic pest that damaged the roots ogrape vines as Phylloxera vastatrix, now called

Daktulosphaira vitifoliae and commonly known

as grape phylloxera. he proboscis (the tubu-lar mouthparts) o grape phylloxera has both acanal rom which it injects venom into the rootsand a eeding tube through which it takes in vinesap and nutrients. As the toxin rom the venomcorrodes the root structure o the vine, the sappressure alls and the pest moves on to a new site.Because this insect pest was rarely seen on a dam-aged plant, as it had already moved on to a healthyroot, it took a number o years or it to be identi-

fied as the problem. It is a native o North Americathat had been brought across the Atlantic on plantmaterial in the nineteenth century.

Controversy over whether this insect really wasthe cause o the problem continued until a thirdscientist, Charles Valentine Riley, confirmed thediagnosis. Riley became an entomologist or theU.S. Department o Agriculture (USDA), wherehe was one o the first to practise biological con-trol when he introduced a beetle to control a scale

insect that was damaging citrus in Caliornia.He confirmed that phylloxera caused damage toEuropean grapes, and he was also the first to notethat the American grape (Vitis labrusca) was resis-tant to the pest.

Many methods o control were triedsprayingchemical insecticides, introducing poultry to eatthe pest, and burying toads under vines to drawout the poison damaging the vinesbut to noavail. wo wine growers, Leo Laliman and Gas-

ton Bazille, first tried grafing the European winevarieties onto the American vine. Although thisproduced plants which were no longer affected

by phylloxera, it was not universally accepted as asolution because it was thought that grafed plantsproduced poorer quality wine than vines grownon their own roots. Te effect on quality o wineis still debated. Cyprus is the only part o Europe

where grapes are still grown on their own roots, asthe island has remained ree rom the pest. I am

not sure i Cyprus is particularly noted as havingsuperior wine to other countries, however.Other ruit crops with pest issues are oten

helped by selecting resistant rootstocks. hewoolly aphid (Eriosoma lanigerum), a pest oapples, can be controlled by using resistant root-stocks. Peach growers in North America usedLovell rootstocks rom the s until a root-knot nematode (Meloidogynespecies) became anincreasing problem in Caliornia. So Nemaguard

was released by the USDA Rootstock BreedingProgram in the s ollowed by Nemared inthe s and Guardian in the s. When a newroot-knot nematode species was ound in Flor-ida to which the previous rootstocks were notully tolerant, a new rootstock, Flordaguard, wasreleased by the University o Florida.

To increase disease resistance

In the early twentieth century, the Citrus Exper-imental Station was set up in Caliornia when aroot rot disease o citrus began to reduce yields,especially in lemon orchards. Above ground,the symptoms are characterized by slow decline,


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moderae lea chlorosis, reduced growh, lacko ree vigour and dieback. hese sympomsare associaed wih exensive canker lesions andgummosis a he base o he runk, as well as rooro, exending rom main roos ino eeder roos.

Gummosis occurs in a number o plans, espe-cially rui rees, as a reacion o damage causedby weaher condiions, inecions, insecs, ormachines. Sap oozes rom wounds or cankersorming paches o a gummy subsance.

In , plan pahologis Howard Fawcet wasappoined o research he causes o hese losses.He idenified aPhytophthora ungus ha causedhe bark o die near soil level, and caused bohgummosis and brown ro o ruis. Several Phy-

tophthoraspecies have been idenified as causalagens, he mos imporan o which are P. cit-rophthoraandP. nicotianaevar.parastica.

Conrol measures using Bordeaux mixure,copper sprays, and surgical excision o lesionshave been used. Furher research ino roosocksshowed ha sour orange (Citrus aurantium)

wasPhytophthoraresisan, and hese were soonbeing used exensively. However, i is imporano ensure he scion is no exposed o he soil or

waer rom he soil, and ungal spray programmesare sill used o preven hese problems leading oinecion.

Resisan, or oleran, roosocks have beenidenified or many oher diseases. For example,alhough sour orange is gummosis resisan, i issuscepible o he virus riseza. Tristeza, he Por-uguese word or sadness, was he name given ohis virus by Brazilian growers, when he diseasescaused he deah o millions o cirus rees in he

s. Citrus jambhiri(rough lemon) and C. sinen-sisPoncirus trifoliata(cirange) would be alerna-ive roosocks or his problem.

Firebligh (Erwinia amylovora) is a major hreao apple and pear orchards, and common roo-socks like M and MM (or apples) and quince

(or pear) are suscepible o his disease. An aler-naive roosock or apples is M, and or pears,a roosock rom he Old Home Farmingdaleseries. In cherries, Col or Maheleb roosocks ol-erae bacerial canker (Pseudomonasspecies), bu

only Maheleb also oleraes crown gall (Agrobac-terium tumefaciens).Alhough grafing is ofen used o conrol dis-

eases, i can also cause disease spread. Psorosis(Caliornia scaly bark) is an incurable graf-rans-missible disease affecing oranges, graperui, andangerine rees. Firs idenified in he weniehcenury, bark scaling is caused by a virus leading odeah o he inner wood and decline in vigour ohe rees ha are affeced. Psorosis was rare among

he seedling rees ha made up Caliornias cirusindusry in he lae nineeenh cenury. However,as grafed rees became commonly used, psorosisspread and became a major problem by he earlywenieh cenury. Once i was demonsraed hahe disease was being ransmited across he graf,measures were inroduced o ensure only cleansock was used or grafing.

To control vigour

In some cases, grafing can improve he vigour ohe scion. For example, Sorbus ariaLuescens isgrafed ono S. intermediaraher han is own spe-cies o give a sronger, more vigorous roo sysem.I is more common, however, o use grafing oconrol vigour, especially in rui crops. Te useo dwarfing roosocks or apples has been knownor many hundreds o years. Paradise, or exam-ple, was named in France in he mid-nineeenh

cenury, bu is hough o have been used since heime o Alexander he Grea. Tere was also a loo variaion in he size o plans produced by wha

was mean o be he same roosock, and, laer inhe nineeenh cenury, clones were idenifiedha were all mean o be Paradise.


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Eas Malling Research Saion in he UniedKingdom (now Eas Malling Research, or EMR)

was esablished in o suppor he rui indus-ry by researching he culural problems o grow-ing ree and bush ruis. Capain R. Wellingon,

he firs direcor and only scienis when he sa-ion opened, sared o collec selecions o appleroosocks o sor ou heir classificaion, es andselec he bes clones, and sandardize hose avail-able o commercial growers. Tis work was jus

beginning when, in , Wellingon lef o servein he Firs World War.

Wellingons work was aken over by RonaldHaton, who successully seleced and classifieda range o commercial roosocks. Iniially hese

were lised by Roman numerals; laer hey werelised by Arabic numerals, all wih he prefix Mor Malling. Some o hese selecions were romlong-used, named roosocks, bu hese were alsoincluded in he numbering sysem. For example,M was a vigorous unnamed culivar, while M

was he vigorous roosock previously namedEnglish Paradise.

Alhough en roosocks were released by EasMalling and have been used worldwide, only wo

are now used commercially: M, a semi-dwarroosock bred around in France and previ-ously called Doucin Reinete or Doucin ver,and M, a dwarfing roosock seleced in inFrance as a chance seedling and named Jaune deMez or Paradis. M is sill he mos imporanroosock being widely used around he world.

In , he John Innes Research Saion a Mer-on joined wih Eas Malling o begin a breedingprogramme o urher improve he available roo-

socks. Te programmes primary goal was o breedor resisance o woolly apple aphids, in addiiono heir vigour characerisics. In he s heMeron Immune Series was released and givenMI numbers () o which only MI issill used. Furher breeding, using Norhern Spy,

a variey ha had resisance o woolly apple aphid,led o a second series being released in . Tis

was designaed he Malling-Meron (MM) seriesand numbered MM. Oher noable roo-socks have been inroduced: M in , M

in , and M in . Eas Malling coninueso research ino improving roosocks, using hewide range o geneic maerial hey have collecedover he years. MM, a semivigorous roosocksimilar o MM bu wih beter resisance ocrown and collar ro, was recenly released. Selec-ions are being made o improve he rooing oM, while reaining is dwarfing characerisicso reduce he need or permanen saking or isuse as an inersock. Fuure selecions may be or

roosocks more resisan o drough or oher cli-maic acors like windier weaher.he dwaring roosock M has signiicanly

changed he managemen o apple orchards,increasing heir cropping poenial. From hes and s, breeding programmes or sweecherry roosocks were begun wih he aim oemulaing he improved orchard managemen and

yields seen in apples. One o hese programmes,a Eas Malling Research, concenraed on crosses

beweenPrunus aviumandP. pseudocerasus.Prunus avium is he radiional roosock orswee cherry, and alhough some selecions have

been made o provide improved clonal roosocks,like F/, hey produced vigorous rees and wereno easy o propagae vegeaively.Prunus pseudoc-erasusis a small flowering cherry ha has dwarfingpoenial, produces roo iniials, and can be propa-gaed rom leafless winer cutings. Unorunaely,i is no compaible as a roosock or cherries.

Crosses were made beween hese wo specieso ry o obain he benefis o each: compaibil-iy wih swee cherry, reduced vigour o he resul-ing ree, and he abiliy o propagae vegeaivelyhe roosock rom cutings. One cross was even-ually seleced and released in he s as a new


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roosock named Col. Available rom he earlys, Col grows o abou percen he heigho Prunus aviumroosocks, has excellen crop-ping poenial, and can be propagaed by leaflesshardwood cutings.

A abou he same ime in Germany, WernerGruppe o he Jusus Liebig Universiy in Giessen,norh o Frankur, sared a breeding programmeor cherry roosocks wih aims similar o hose ohe Eas Malling programme. UsingPrunus aviumas one paren, he and his assisan Hanna Schmidmade around six housand crosses wih a rangeo dwar cherry species. Ou o hese, P. canescensproved o be he mos promising species, and

several selecions o seedlings rom his crosswere made. he wo ha proved mos worhywere named Gisela and Gisela respecively.Alhough Gisela is a girls name in Germany, iacually sands or Giessens selecion orP. avium

(GISELA).Gisela was he more dwarfing, abou halhe ree volume o Col roosock, bu croppedas heavily. Gisela is as vigorous as Col, buhas wice he cropping poenial and is repor-edly more regular in bearing. Gisela gives hepoenial o grow cherries under proecion, ina similar way ha has been developed or sofrui in recen years. Tis opens up new cropping

Sweet cherry trees growing on the dwarfing Gisela 5 rootstock under protection at Castleton Farm

near Aberdeen in northeastern Scotland. Without the dwarfing rootstocks making protected

production possible, cherries could not be grown commercially this far north.


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opportunities and markets or cherries. Te onlyissue with Gisela is that it is not as easy to propa-gate as is Colt.

he way in which vigour control occurs isstill poorly understood, but could be due to the

way roots send signals to the top o the plantthrough hormone and mineral transport throughthe xylem. Or, it could be the capacity or wateruptake and transport through the plant.

Recent experiments showed that resistance tosap flow imposed by the graf union and at therootstock shanks, was greatest in the highly dwar-ing M rootstock. In the dwarfing M, resistanceis intermediate and in the semi-dwarfing MM,it is least. Tis suggests that in apples, sap flow

affects tree vigour, but this may not be the mecha-nism or all dwarfing ruit rootstocks.

To adapt to soil pH

Rhododendrons are ericaceous plants that nor-mally grow in organic acidic soils o pH ...Growing these plants in alkali soils requires thecreation o raised beds, lined to isolate them romthe natural soil, and filled with a low-pH ericace-

ous medium. Irrigation is by rainwater, and che-lated iron (Sequestrene is one brand) should beused i the leaves start to yellow (lime-inducedchlorosis). Tis is all very time consuming andhard work or the average gardener.

owards the end o the twentieth century, asel-seeded rhododendron was ound growing ina quarry with a known alkali soil and bedrock. Aconsortium o German nurseries crossed thisplant with a standard rhododendron rootstock,

namely, Rhododendron Cunninghams White.Te aim was to obtain a new rootstock that wouldhave the lime-tolerant characteristics o the seed-ling and the compatible grafing ability o Cun-ninghams White. In addition to these two quali-ties, seedlings were selected or their habit, vigour,

root development, hardiness, and lack o sucker-ing. Te result was the new rootstock Inkarho,

which grows in soils with a pH up to at least .and which can withstand cold to C. It alsoseems to grow well in exposed conditions and

even tolerates clay soils.

To survive waterlogging

Te arboretum at North Carolina State Univer-sity has carried out adaptability trials o speciesrom around the world. Tese have shown thatroot survival under wet, hot summer conditionsis the single most important actor in trees that arenot native to the area. Respiration rates rise in hot

conditions, requiring more oxygen or the roots.Unique to the southeastern United States is thesudden flooding o poorly drained soils that cancreate temporary, but atal, anaerobic conditionsor roots. Further west, soil temperatures are high,

but soils are drier and oxygen depletion does notoccur. Further north, soil temperatures are lower,

but rain occurs in cooler conditions, so that anaer-obic conditions do not develop.

In the past, rootstocks or grafed ornamentals

have been selected only or compatability andavailability, but the University now suggests thatsuch rootstocks are not always suitable or climates

with wet, hot summers. For example,Abiesspeciesare used as Christmas trees and so are required inlarge numbers and at low cost. Tey are grafedontoA. balsameaorA. faserito keep costs down,

but have weak root systems that do not survive inthe poorly drained soils o the U.S. Southeast.

Cornus Eddies White Wonder grows well in

the cool, wet Pacific Northwest, but cannot growin the Southeast. Initially this dogwood cultivarwas thought to be unsuitable or the Southeast,but it is now known that the rootstock (C. nut-tallii) is the problem. Cornus floridamay be a bet-ter rootstock in the Southeast.


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To create unique versionsof favourite plants

Te chrysanhemum is he symbol o auumn inJapan, where i holds a special place in he coun-

rys culure. I originaed in China and is hougho have been inroduced o Japan in he eighhcenury . In he hireenh cenury, he reiredemperor Gooba ashioned a sword wih a chry-sanhemum flower moi. Te flower became hesymbol o he Japanese imperial household andhe Chrysanhemum Trone is he Sea o heEmperor. Chrysanhemum Day occurs on heninh day o he ninh monh, and i was a radi-ion on his day or people o use clohs o wipe

dew rom he chrysanhemum on heir skin, as away o mainaining heir youh.

Te chrysanhemum, or kiku in Japan, eauresin displays in Buddhis emples in he auumn. Iis eiher grown on single sems as a single bloomor grafed so ha he resuling plan can be rainedino a dome, shield, or differen shape. Te roo-

socks used o give chrysanhemums a srong roosysem ha oleraes high summer emperauresand is disease and pes resisance is Artemisiaannua, A. figida, or A. scoparia. Grafing allowsmore han one scion o be used so ha differencolours appear on he shapes produced and i cre-aes sems ha are more flexible and hus able o

be rained around he rames.

To obtain special forms

of plant growth

Producing small rees by grafing ono all roo-socks has been carried ou or many years and

was paricularly popular in Vicorian gardenswhere sandard roses, broom (Cytisus), andoher shrubs, were widely used. A his ime heKilmarnock willow (Salix capreaKilmarnock),he male orm o S. capreaPendula, was oundand inroduced ino commerce. In early ,

a dwar weeping orm o S. caprea(goa willow)was ound on he banks o he River Ayr in souh-wesern Scoland, eiher by an unknown boa-nis or by Tomas Lang (), a nursery-man and seedsman rom Kilmarnock, Scoland.Lang named he new orm afer his homeown.

Alhough he Kimarnock willow could be prop-agaed by cutings, o obain he required growhhabi i needed o be grafed ono he op o a allroosock. A specimen was planed in he Royal

Boanic Gardens, Kew, where i was noiced byhe horiculural world. I was soon in demand,and by he lae nineeenh and early weniehcenuries his hardy, aracive small ree had

become (and remains) popular or parks, aroundwaer eaures, and in small gardens.

Grafted chrysanthemum in shield shape at

Naritasan Shinshoji Temple, Narita, Japan.


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Salix capreaKilmarnock (left) in late winter

just starting to show the catkins.

Tree gooseberries using Ribes aureumas the

rootstock allow more air movement around

a plant than a bush form does, which in turn

may reduce mildew and is easier to pick .

Wih he adven o package holidays rom heUnied Kingdom o Spain in he s, he gar-den has been increasingly used as an oudoorroom, and eaing al resco has become popular.

Alhough no new, his led o a demand or paio

plans, small sandard rees produced rom shrubslike CotoneasterandEuonymus, grafed in a simi-lar way o he Kilmarnock willow, o enhance heappearance o he paio area.

Culivaion o rui o he genus Ribesbegan inEurope in he sixeenh cenury and was inro-duced o Norh America by he lae eigheenhcenury. In he nineeenh cenury, ree culure bygrafing Ribeswas common. In paricular, goose-

berries were grown by his mehod, as hey can be

difficul o propagae by hardwood cutings, com-pared wih currans like blackcurrans. Raising he

canopy by grafing he scion ono sems cm all makes weed conrol easier, reduces heincidence o powdery mildew, and can be used omechanize harvesing wih over-he-row harves-ers. Te roosock used is R. aureumBrech or R.aureumPallagi . Boh are medium-sized shrubsha have vigorous growh and litle suckering.

In he Unied Saes, a ederal ban on culivaiono Ribesspecies was imposed in he early weni-eh cenury, since he plans serve as an alerna-ive hos or whie pine bliser rus ha severelyaffecsPinus strobus(whie pine), an economicallyimporan oresry ree o he ime. Alhough he

ban was removed in , curren producion oRibesin he Unied Saes is sill on a small scale

and he ban on blackcurran growing is sill inplace in many saes.


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In Europe, especially Hungary, ree gooseber-ries were popular ino he s, bu are no longerused or commercial producion. Grafed curransand gooseberries are sill available or he amaeurgardener, however, and are worhy o being used

more widely.Te radiional grafing echnique recommendedor gooseberries is a litle unusual and is describedas green grafing. Te roosock is propagaed bymound layering, and he graf is carried ou in hesummer when he roosock is cm all, sillatached o he moher plan, and boh sock andscion are abou mm in diameer. Grafing whenhe sock is sill acively growing (green grafing)is more successul han waiing unil he sock is

ully maure and dorman. A splice or whip-and-ongue graf is used and secured wih polyheneape o seal he wounds.

To gain the benefits of interstocks

Prunasin is one o several cyanogenic glycosidesound in many plans, especially hose o he roseamily. Tese glycosides are inacive moleculesha are sored in he vacuoles o plans. I he

plan is atacked, he glycoside is released and isacivaed by enzymes in he cyoplasm, producinghe oxic hydrogen cyanide (previously knownas prussic acid). Tis makes a valuable deencemechanism agains pes aacks. For example,maize is suscepible o damage by rooworms(Diabrotica species), while he relaed sorghumconains glycoside in is roos ha makes i resis-an o his pes. Prunasin is ound inPrunusandOliniaspecies and gives he biter ase o dande-

lion coffee, a coffee subsiue, as well as in Cydo-nia oblonga(quince), which is used as a roosockorPyrus communis(European pear).

Grafing pear ono quince is an unusual com-binaion, as i is rare or grafs beween differengenera o be successul. Alhough a successul

Tree redcurrants make an attractive

patio plant in their own right.

Tree blackcurrants.


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union is usually ormed, over pear culivarshave been shown o produce delayed incompai-

biliy. Ta is, he ree may grow or yearsbu loses vigour and dies when i should be a ispeak o rui producion. Graf incompaibiliy is

discussed urher elsewhere in his book, bu hesoluion o his ype o incompaibiliy is o use aninersock beween he scion and roosock.

he reason or pear-quince incompaibiliy isone o he ew ha has been ully explained. Pearsdo no conain prunasin, and once hey are grafedono quince, he prunasin is ranslocaed up o hepear issue. Afer he prunasin leaves he plans

vacuoles, i becomes acivaed by enzymes in hecyoplasm o produce hydrogen cyanide. In com-

paible grafs, he pear culivars conain a waer-sol-uble inhibior o he enzyme ha caalyzes hebreakdown o prunasin, and so he sage o aciva-ing hydrogen cyanide does no occur. Where hisinhibior is lacking and he cyanide is produced,cambial aciviy is reduced a he graf union, andphloem cells are desroyed around he union.

he aciviy o prunasin is also emperauredependen, wih he opimum emperaure beingC and no aciviy occurring over winer. Te

graed plan is hereore damaged during hesummer, bu he cells can repair, and he phloemand cambial connecions re-esablish during he

winer, when no prunasin is produced. Tere is,hereore, a cycle o weakening and repair hadelays he final ailure o he graf. In cooler cli-maes, graf ailure can be delayed or many years,

while in warmer climaes graf ailure will occurmore quickly.

o overcome his incompaibiliy, an inersock

needs o be used ha is compaible wih bohscion and roosock and hus will conain heinhibior. Te wo mos commonly used iner-socks are Beurre Hardy or Feriliy.

M is he mos common dwaring roo-sock used in apple producion in Europe and

increasingly in Norh America. I can easily bekep o m high and sars o crop soon aferplaning, producing large rui and excellen oal

yield. I is, however, difficul o propagae and pro-duces ewer shoos in a sool bed han oher roo-

socks. Te roo sysem also develops slowly andhe rees mus be permanenly saked. In addiion,alhough i is resisan o collar ro, i is suscepibleo firebligh, woolly apple aphid, crown gall, andmildew. Breeding programmes are rying o over-come some o he disadvanages o his roosock,

while reaining is atribues. Sill, M can be usedas an inersock wih good success.

In graing, he vigour o he roo sysem isimporan in conrolling vigour, bu i has been

ound ha M sill has a dwarfing effec whenused as an inersock, especially i long inersockpieces are used. Alhough he dwarfing effec isreduced when M is grafed ono a more vigor-ous roosock, i sill produces mos o he ben-efis o yield and qualiy previously described. Iis hereore possible o use MM as a roosock

wih M as he inersock. MM is a new roo-sock ha will give he benefis o a sronger roosysem han M, which produces a shallow roo

sysem requiring o be suppored by saking inhe orchard. In addiion, MM will give greaerresisance o apple pess and diseases han M.

Inersocks can also be used o inroduce cold ordisease resisance. In rubber producion in Brazil,or example, Hevea brasiliensis(rubber ree) has

been affeced by lea bligh, bu using a resisaninersock can reduce his. In roses, Rosa rugosa(hedging rose) was he main roosock or san-dard roses, bu was affeced by disease problems.

One soluion is o use a roosock like R. dumeto-rumLaxa, normally used or bush roses. An iner-sock like R. multiflorade la Grifferaie is buddedono Laxa and grown up o orm he sem o hesandard rose. Te scion o he flowering rose ishen budded ono he inersock.


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Ye anoher use o an inersock is o producean ornamenal ree.PrunusincamOkam is anatracive flowering cherry ha produces masseso carmine-rose flowers in early o midspring andatracive oliage colour in auumn. Over summer

and winer, however, here is no much o rec-ommend i. Insering an inersock o P. serrula(ibean cherry) adds a runk wih shining cop-pery brown, young bark ha peels away in bands,giving year-round appeal. TeP. serrulainersockis grafed ono a Col roosock, and a sem isgrown up o a mere long.PrunusincamOkamis hen grafed on op o he sem.

To change existing varieties

of trees

Frui orchards are long-erm invesmens, andalhough culivars will be careully seleced, heymay no prove o be he bes or changing mar-kes, or an orchardis may simple wan o grownew culivars wih improved rui characerisics.Tis is where op-working may be used o changeculivars in an orchard wihou grubbing ou heexising rees and saring again. op-working can

also be used o graf a pollinaor culivar ono reesha lack proper pollinaion. I is also possible ograf several culivars ono one ree as a novely,alhough his would no be done or commercialrui producion.

In lae winer, selec six o en limbs owardshe base o he ree. Tese should be seleced ogive a sub o cm in diameer once cu back,and orm a good ramework or he uure ree.Branches higher up he ree are reained o pro-

vide shade o he new gras and mainain hegrowh o he ree during he nex season. Eihera clef graf or inlay graf is used, since he scionhas a much smaller diameer han he sub. wo ohree scions are hen grafed ono each sub. Aferhe firs year, he successul grafs will have sared

Single stem of PrunusincamOkam grafted onto Colt.

The new plant has attractive pink flowers in spring.

Prunus serrulagrafted onto Colt rootstocks to produce

a 1-m stem with P.incamOkam grafted on top.

The attractive bark of P. serrulaprovides more year-

round interest than P.incamOkam used by itself.


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o grow and all bu one should be pruned back oneach sub o orm he new main branches.

Unworked branches should also be removedafer he firs year unless he original ree is morehan eigh years old. In his case, he graing

should be carried ou over a ew years wih abouwo-hirds o he branches grafed in he firs year.Te hard pruning o he ree will promoe waershoos o be produced. Some o hese can belef emporarily o shade he new branches, bushould be removed afer one season. In his way,culivars can be changed on an exising ree overa ew years. o add a pollinaor, only one branchrequires o be pruned back and he seleced sciongrafed ono his.

To repair damaged trees

Bridge-grafing can be used where he bark o abranch or main sem has been damaged, causinghe bark o be ringed, prevening he movemeno waer and nuriens hrough he phloem and

xylem. Inlay grafs are used or his, ataching hescion boh above and below he damaged area.Te scions hemselves are rom shoos o he cor-

rec diameer rom he same ree. Tis ype ografing is bes carried ou in he spring jus beoreflowering, and several scions are atached aroundhe sem so ha once he union is ormed he newgrowh will be even.

To produce artistic formsvia inosculation

Husband and wie, or marriage rees, are recorded

in some counries like China, Japan, Georgia, andScoland. I is believed ha branches were delib-eraely grafed ogeher beween rees (inoscula-ion) o symbolize he unificaion o wo peoplein marriage. A he now-abandoned LynncraigFarm near Dalry in Ayrshire are wo crab apple

rees (Malus sylvestris) grafed ogeher in whawould have been he armhouse garden. Anoherexample in Ayrshire is a Eglinon Counry Park,

where a sessile oak (Quercus petraea) on an islandin he fishpond appears o have been deliberaely

grafed. In Tomas Garnets long-winded Obser-vations on a our Trough the Highlands and Partof the Western Isles of Scotland, published in ,a marriage ree was skeched a Inverary in Argyll-shire, ormed rom wo sems o a lime ree (iliaeuropaea).

Tis pracice became more elaborae o producea range o orms by grafing. Called arbosculpure,i is he ar and echnique o growing sems o rees

by bending, pruning, or grafing ino a variey o

orms. An early exponen o his ar orm was JohnKrubsack (), a bank presiden, armer,

A marriage tree at the now-abandoned Lynncraig

Farm near Dalry in Ayrshire. Two crab apples (Malus

sylvestris) have been grafted together to form a heart

shape in what would have been the farmhouse garden.


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nauralis, and landscaper rom Wisconsin. Healso made urniure rom wood ound around hispropery, bu he decided he could grow a piece ourniure ha would be sronger han anyhing hecould make. He evenually grafed rees ogeher

o orm a sea.Tis ar orm, however, probably reached ispeak when, in , Alex Erlandson sared omake seas, baskes, and many absrac orms bygrafing rees and branches ogeher. For example,his Baske ree is made rom six sycamore rees(Acer pseudoplatanus) grafed ogeher wih differen connecions o give a baske shape. Alexdecided o make some money rom hese sculp-ures and opened ree Circus, a ouris atrac-

ion ouside Sana Cruz, Caliornia. Alhough i

became quie amous boh in he Unied Saesand abroad, i was no very profiable, and Alexappears only o have made abou hree hundreddollars a year rom his venure. In , he soldhis collecion o sculpures or welve housand

dollars. Over he years, hese sculpures declinedhrough neglec unil he s when Mark Pri-mark, a local archiec, began a campaign o savehe rees. Evenually Mark received he help oMichael Bonane who was building a heme parkin Gilroy, miles rom Sana Cruz. In , heremaining rees were lied and moved o Gil-roy Gardens where o he original sculpuressurvive.

Alhough hese are exreme examples, arbo-

sculpures are commonly seen. For example,sems o Ficus benjaminaha have been pleaedogeher are ofen seen in shopping cenres.

To screen plantsfor disease indexing

Grafing can be used in disease indexing, wherelaen (unseen) viruses may be presen in oneplan culivar ha can hen inec oher culivars

known o be suscepible o he viral disease. Teplan hough o conain he laen virus is grafedono a suscepible plan. I he virus is presen,hen i will be ransmited o he suscepible planand sympoms will be seen. he es does norequire he ormaion o a permanen union.

In , a new disease sared o inec chrysan-hemums growing in greenhouses in he UniedSaes and Canada. Wihin ive years, raes oinecion were as high as percen and

hreaening he uure o he indusry. Te dis-ease was ideniied as chrysanhemum sunvirus. Plan pahologiss rom Cornell Universiy,he USDA, and a commercial company, Yoder,

worked o develop echniques ha could be usedpracically o ideniy he virus. Tey did his by

In this elaborate form of arbosculpture, stems of Ficus

species were spiralled around wire hoops until they

grafted together to produce a permanent, open shape.


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grafing suspeced plans ono indicaor plans,and his ormed he basis or a cerificaion pro-gramme ha conrols he disease oday.

his screening mehod has now been super-seded by do-blo hybridizaion (RNA) and a

polymerase chain reacion known as PCR. Graf-ing can sill be used o indicae disease problems,however. A presen, ash dieback (Chalara fax-inea) is causing major losses in his imporanree species. Atemps are being made in Europeo breed or selec culivars ha are resisan o hedisease. In Germany, Heinrich Loesing, direc-or o Versuchs und Beraungsring Baumschulen(Research and Advisory Associaion or Nurs-eries), near Hamburg, has chip budded secions

rom diseased plans ono hese new selecions oes i hey ruly are resisan. Unorunaely, manyare no proving as resilien o he disease as washoped.

To micrograft

Te only ruly novel mehod o grafing devel-oped in he wenieh cenury was micrografing,a echnique adaped rom plan issue culure (he

asepic culure o cells, issues, organs, and heircomponens under defined physical and chemi-cal condiions in serile condiions). In , ahe German Academy o Science, Gotlieb Haber-land presened his experimens in he culure osingle plan cells. Tis led o echniques o sudyhe growh and ineracion o cells in conrolledcondiions. In he s, Roger Gauhere, heFrench biologis rom he Faculy o Sciencein Paris, produced he firs rue plan issue cul-

ures rom cambial issue o sycamore (Acerpseudoplatanus).In he s and s, significan progress was

made in growing plans in vitro. Swedish-bornAmerican Folke Skoog progressed he under-sanding o plan growh regulaors, especially

cyokinin. He hen ook on a docoral suden,oshio Murashige, o look or an undiscoveredgrowh hormone in obacco. Tis search provedruiless, bu he deailed analysis o he con-siuens o juiced and ashed obacco led o an

improved ormula or he medium used or issueculure. Known as Murashige and Skoog ormula,i remains he basis o ormula used in plan issueculure oday.

O more imporance o horiculure, his or-mula mean ha issue culure could move rom

being jus an experimenal ool or plan biolo-giss o a pracical mehod o plan propagaion.Micropropagaion enables he rapid muliplica-ion o plans. For example, new culivars o rho-

dodendrons, roses, or oher shrubs ha would

A chip from a diseased tree is grafted onto a healthy

plant to test for resistance to ash dieback (Chalara

fraxinea). Unfortunately, this tree is not resistant.


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ake en or more years o bulk up by convenional

echniques can be produced in large numbers in

one or wo years by micropropagaion. Te ech-

nique is also very imporan in he propagaion o

orchids ha are now such popular houseplans.

One paricularly valuable applicaion o micro-propagaion is in he firs sage o producing very

healhy plans, especially poaoes, rui, and

oher ood crops. Viruses and oher sysemic dis-

eases can usually be eliminaed rom a plan by

he use o hermoherapy and apical merisem

culure. By growing he original plan a C,

disease-ree maerial can usually be obained by

removing he op . mm o he merisem and cul-

uring his in vitro. Wih rui like srawberries and

raspberries, hese shoos can hen be muliplied inculure, and once enough plans have been grown,

hey can be induced o roo and weaned back ino

naural growing condiions.

Micrograing has been developed or cirus

plans because he scion maerial will no produce

is own roos. In his case, seedlings o roosocks

are grown in vitroand he small shoo ip o he

scion maerial is hen removed o be grafed ono

he roosock. A riangular or cu is made on

he op o he seedling, and he scion shoo ip is

placed on op. Te procedure is carried ou on a

serile bench, called a lamina flow cabine, o pre-

ven conaminaion, and hen he graf is placed

back ino he culure ube. Once he micrografhas sared o grow and i is known o be ree o

viruses, - o -cm-long shoos o he scion are

re-grafed ono convenionally grown seedlings

ha are grown on in naural condiions. Tis very

specialized procedure has proved invaluable o he

cirus indusry.

Tere have been oher applicaions o micro-

grafing used recenly. Foresry has micrografed

coniers, especially old rees ha have paricular

value. Micrografing is being used o propagaehese plans vegeaively o increase heir num-

ber and reurn hem o a more juvenile sage. I is

hoped ha his maerial can hen be propagaed

by cutings o provide plans or a seed orchard.

Micrografing is also used by research scieniss o

invesigae aspecs o plan physiology like graf

incompaibiliy.

The Manual of Plant Grafting: Excerpt

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Transcript of The Manual of Plant Grafting: Excerpt