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RHS PLANT TRIALS BULLETIN Number 23 December 2008 RHS PLANT TRIALS BULLETIN Number 23 December 2008 Hydrangea paniculata Neil Lancaster Botanist, RHS Garden Wisley Wendy Wesley Trials Officer, RHS Garden Wisley Hydrangea paniculata Neil Lancaster Botanist, RHS Garden Wisley Wendy Wesley Trials Officer, RHS Garden Wisley

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RHS PLANT TRIALS BULLETINNumber 23 December 2008

RHS PLANT TRIALS BULLETINNumber 23 December 2008

Hydrangea paniculataNeil LancasterBotanist, RHS Garden Wisley

Wendy WesleyTrials Officer, RHS Garden Wisley

Hydrangea paniculataNeil LancasterBotanist, RHS Garden Wisley

Wendy WesleyTrials Officer, RHS Garden Wisley

H. paniculata in the wild and incultivationH. paniculata is native of cool temperate and sub-tropicalregions of Japan, China and Sakhalin, where it grows as adeciduous shrub or small tree to 8m in height, at altitudesto about 1300m. It is often stated to be a very variablespecies in the wild, but not all authors agree on this.

H. paniculata was first described and named in 1829 by theGerman physician and botanist Philipp Franz von Sieboldwhile working for the Dutch East India Company based onDeshima Island within Nagasaki harbour, Japan. Grantedlimited access to the mainland to carry out his medicalduties, at a time when other foreigners were excluded,Siebold used the opportunity to collect and describe thenative plants, including H. paniculata. Siebold’sdetermination to explore this closed country eventuallyresulted in him falling foul of the authorities and he wasbanished from Japan before the plant could be exported toEurope. Fortunately, he was allowed to return 30 yearslater, when he succeeded in sending back the cultivatedform of H. paniculata now known as ‘Grandiflora’. Thiscultivar, also known as the pee gee hydrangea, is probablystill the most widely grown.

Other early introductions from Japan include ‘Floribunda’,discovered by Carl Maximowicz in a Japanese nursery inthe 1860s, ‘Praecox’, raised from seeds collected onHokkaido Island by Charles Sargent in 1897, and ‘Kyushu’,introduced as a wild-collected seedling from Kyushu Islandby Collingwood Ingram in 1926.

In the 1950s, at the embryonic Kalmthout Arboretum andlater at Hemelrijk, Robert and Jelena de Belder began toexperiment with raising and selecting seedlings ofH. paniculata, derived initially from an old plant in theirgarden of ‘Floribunda’. The first and most famous of these,

Background to the trialAlthough Hydrangea paniculata has been cultivated inEuropean gardens for well over a century, for most of thatperiod there has been little choice beyond a handful ofvery early introductions. H. paniculata, the panicledhydrangea, has invariably played second fiddle to the morecolourful H. macrophylla, or hortensia, even though it isgenerally easier to grow and more reliably hardy. The firstedition of Michael Haworth-Booth’s The Hydrangeas,published in 1950, included over 300 hortensias, but only3 types of H. paniculata, namely the cultivars ‘Floribunda’,‘Grandiflora’ and ‘Praecox’.

After the 1950s, the range of cultivars started to increasewith the appearance of the first de Belder introductionsand slowly gathered pace in the 1970s and 1980s as newgenerations of seedlings were raised from existing cultivars.Because of the long lead-time for raising and introducingnew plants, only eight cultivars could be listed in the firstedition of the RHS Plant Finder in 1987. A decade on, therewere still only twelve cultivars, four of the early de Belderselections having become more widely available, butsubsequent years saw a more rapid increase. In the past 10years, interest in H. paniculata has taken off with manypromising new introductions from breeders in Belgium,Holland, France and the USA.

With so many new cultivars coming on to the market, theRHS decided to hold a trial to compare the new cultivarswith the old and to select the best ones for the Award ofGarden Merit. More than 40 cultivars were assembled in atrial that was considered by many of those involved to beamong the most successful woody plant trials yetundertaken by the RHS. At the same time, the first Eurotrialswere conducted in the UK, France, Germany and Holland,providing an interesting opportunity to compare trial resultsbetween different sites and growing conditions.

The RHS Trial of Hydrangea paniculata

RHS Plant Trials Bulletin2

Front cover:Hydrangea paniculata‘Limelight’

Right: Hydrangeapaniculata TrialAugust 2008

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‘Unique’, was reputedly the sole survivor of a batch ofyoung seedlings that had been ravaged by blackbirds. Itturned out to be an exceptional plant whose offspringyielded many good new cultivars, including ‘Papillon’,‘White Lace’, PINK DIAMOND, ‘Burgundy Lace’, ‘BrusselsLace’, ‘White Moth’, ‘Green Spire’ and ‘Melody’. Furthergenerations were raised in the 1970s and 1980s by openpollination of these plants, with PINK DIAMOND and ‘WhiteMoth’, in particular, producing some notable cultivars. Thearboretum at Hemelrijk still contains many unnamedplants, and seeds from these are still collected anddistributed to nurseries in the hope of raising new cultivars.

Breeders in Europe and the USA have built upon the deBelder legacy, producing cultivars with inflorescences ofsubtly different shapes and shades of pink, white andgreen, as well as cultivars of more compact habit. Some ofthe most striking new cultivars have been raised by PeterZwijnenburg at Boskoop, including ‘Big Ben’, ‘Phantom’,‘Limelight’, ‘Dolly’, ‘Silver Dollar’ and ‘Pink Lady’, whilesignificant contributions have also come from Darthuizerin the Netherlands and Michael Dirr in the USA.

As a garden plant, H. paniculata has a number ofadvantages over H. macrophylla. It is relatively drought-tolerant, does well in both full sun and partial shade andgrows in acid or alkaline soil, as long as the ground is well-drained. Importantly, it is very hardy (to about -30˚C inthe USA) and as it always flowers on the current season’swood, it is not susceptible to late spring frosts.

Botanical DescriptionHydrangea paniculata is a deciduous woody plant withserrate leaves arranged in opposite pairs or clusters ofthree, and flower heads made up of showy, sterile flowersmixed with smaller, fertile flowers. What sets it apart fromother species is the structure of the inflorescence, which istypically a cone-shaped panicle. The only other Hydrangeathat has flowers arranged in a panicle is H. arborescens andthat is distinguished by having lobed leaves.

Habit: In the wild may be a lax shrub to about 2m or asmall tree to 8m.

Shoots: Somewhat brittle. Downy at first, becominghairless.

Leaves: Elliptic or ovate, serrate, acuminate, rounded ortapered at the base, 7.5 – 15cm long and about half aswide. Arranged in opposite pairs, or in 3’s. Sparselypubescent above and on the veins below.

Flowers: A mixture of small, yellowish fertile flowers andlong-lasting (up to about 8 weeks) sterile flowers with 4 or5 white sepals, usually entire, often ageing to pink orpurplish-pink, particularly on the underside. Flowers areborne in panicles on the current season’s growth, openingfrom the base toward the apex of the panicle. The ovary issemi-inferior.

Fruit: A many-seeded capsule. The seeds have no dormancyand typically germinate in 2 to 4 weeks.

Inflorescence of Hydrangea paniculatashowing pink late season colour

Objectives� To compare and assess new and old cultivars

� To recommend the Award of Garden Merit to thoseconsidered to be the best

� To determine correct nomenclature

� To obtain specimens, photographs, and descriptions as arecord to be held in the RHS Herbarium at Wisley

Records� Habit

� Response to pruning

� Stem colour

� Foliage colour (summer and autumn)

� Flowering period

� Inflorescence shape

� Flower colour (early, mid-season and late season)

Entries68 entries, representing 47 cultivars, were submitted bygardens, nurserymen and individuals in the UK,Netherlands, Belgium and the USA. Details of each cultivarare given in the Selection Table below.

CultivationThree plants of each entry were planted in May 2004. Allplants were cut down to the base after planting. The plantswere grown in the open, with no shade, and watered onlyduring periods of drought. Soil analyses were conductedannually and treatments applied as necessary to eliminatenutrient deficiencies and maintain approximately neutralconditions.

PruningAll plants were pruned each year in late March. The threeplants of each cultivar were used to test three pruningregimes:

1 Hard pruning (to two buds)

2 Moderate pruning (to four buds)

3 Light pruning (removal of previous year’s flowerheadsonly)

The Trial

RHS Plant Trials Bulletin4

Hydrangea paniculata ‘Big Ben’ AGM(H4) 2008

Hydrangea paniculata ‘Floribunda’ AGM H4) 1993*

Hydrangea paniculata ‘Grandiflora’ AGM(H4) 1993*

Hydrangea paniculata ‘Kyushu’ AGM (H4) 1993

Hydrangea paniculata ‘Limelight’ PBR AGM(H4) 2008

Hydrangea paniculata ‘Phantom’ AGM(H4) 2008

Hydrangea paniculata AGM(H4) 1993PINK DIAMOND ‘Interhydia’

Hydrangea paniculata AGM(H4) 2008PINKY-WINKY ‘Dvppinky’ PBR

Hydrangea paniculata ‘Silver Dollar’ AGM(H4) 2008

Hydrangea paniculata ‘Unique’ AGM (H4) 1993*

* Recommended to be rescinded at the AGM Reviewin 2012

The following will receive an Award of Garden Meritwhen available to the public

Hydrangea paniculata ‘Dolly’

Hydrangea paniculata ‘Pink Lady’

Hardiness ratingH4 = hardy throughout the British Isles

Judging CriteriaThe Woody Plant Trials Subcommittee assessedentries in the trial for the Award of Garden Meritusing the following criteria:

� Habit

� Bud / Flower / Faded flower

� Floppiness of head

� Foliage

The AGM is only awarded to plants that are:

� Excellent for garden decoration

� Available from nurseries

� Reasonably resistant to pests and diseases

� Of good constitution

� Essentially stable in form and colour

� Reasonably easy to grow

Award of Garden Merit (AGM)

Hydrangea paniculata Trial September 2007

Where there was a response to pruning, the lightly prunedplants were the first to flower and carried more, smallerflowers than the hard-pruned plants, which flowered later,and bore larger, fewer panicles. Those plants subjected tomoderate pruning were intermediate in panicle size andtime of flowering. Although the hard-pruned plants tendedto grow with added vigour, their larger flowerheads were notalways advantageous, sometimes producing panicles thatcould not be supported and flopped.

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3 Light pruning (removal of previous year’sflowerheads only)

2 Moderate pruning (to four buds)

1 Hard pruning (to two buds)

Light Moderate Hard

February March April

A further pruning demonstration using spare plants was setup in which three plants of each cultivar were medium-pruned at the end of February, March and April. Delayingpruning was found to delay flowering, as illustrated above.

Both techniques proved to be of interest, the firstproducing varying bloom size and a flowering delay, thesecond bringing forward or delaying flowering so as toprovide a succession of blooms. Either could be used toextend the period of flowering for group plantings. It mayalso be worth trying more than one technique on thedifferent stems of a single plant, though this was notattempted during the trial period.

Hydrangea paniculata ‘Floribunda’

AGM (H4) 1993*

Habit: Upright to spreading,190 � 210cm.Foliage: Dark green 147A, leaves inwhorls of three.Stem: Pale in upper inflorescencegrading through purplish pink 186Ain lower inflorescence to brown 177Bon mature wood.Panicle: Half open, conical.Fertile floret: Buds tipped pink.Sterile floret: Greyed yellow 160C,maturing to white NN155A.Scent: Spicy.Flowering: From late July to earlySeptember.Comments: Slender pointed panicles.Will grow into a small tree if unprunedbut suitable for a small garden withpruning.

Hydrangea paniculata ‘Grandiflora’

AGM (H4)1993*

Habit: Sparse and drooping,100 � 130cms.Foliage: Yellow green, much bluergreen than 146B.Stem: Green 147D flushed 186C inlower inflorescence, maturing to midbrown.Panicle: Very dense, conical andtapered. Upper panicle has numeroussmall, pinkish red 47B buds.Fertile floret: Buds strongly flushedpink 55C, petals white, anthers pink.Sterile floret: Lime green 149B,maturing through greyed yellow 160Dto white with pink bosses.Scent: Slightly scented.Flowering: From end of July to earlyOctober.Comments: Stems have a tendency toflop due to heavy, very dense panicles.Improves with age. Not as good as‘Phantom’.

Hydrangea paniculata ‘Big Ben’

AGM(H4)2008

Habit: Upright and slightly spreading,170 � 180cm.Foliage: Yellow green 146B.Stem: Flushed greyed reddish purple186A, lower stem brown approx.200D.Panicle: Half open, conical andtapered.Fertile floret: Pink in bud opening towhite.Sterile floret: Opening pale greenapprox. 154D, becoming white with ahint of green, eye white, sometimesflushed pale pink, maturing to deeppink, slightly deeper than186A.Scent: Strongly scented.Flowering: from early August to midOctober.Comments: Outstanding, very freeflowering. Attractive red stems, flowergoes off to a good pink. Interestinginflorescence with leaves between theflorets. Differences in pruning regimeappear to have little impact.

Hydrangea paniculata ‘Dolly’

AGM subject to availability

Habit: Upright and spreading,165 � 160 cm.Foliage: Yellow green between 137B-C.Stem: Pale green approximately 148Cwith white lenticels; mature woodsilvery brown mixture of 199A-N199C.Panicle: Half open, conical andtapered.Fertile floret: White or creamy greenbuds, flowers white, anthers palecream.Sterile floret: Greenish yellow145A/150C, opening to white withcentral yellow (paler than 151A) flush.Flowering: From late July to late Sept.Comments: Good, undulate, green leaf.Delightfully shaped florets of an attractivecreamy colour in the early stages. Hashuge character. Very impressive, providinga succession of flowers.

AGM descriptions

RHS Plant Trials Bulletin6

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Hydrangea paniculata ‘Phantom’

AGM(H4)2008

Habit: Upright to spreading,145 � 195cm.Foliage: Yellow green, a little greenerthan 146A.Stem: Green 147D flushed 186A,strongly so in lower inflorescence,maturing to mid brown.Panicle: Very dense, conical androunded.Fertile floret: Buds flushed pink, petalswhite, anthers pale pink to white.Sterile floret: Immature sterile floretgreyed yellow 160C, maturingthrough 160D to white with someflorets flushed lime green, deep pinkat maturity. Some florets with fertileflowers in centre.Flowering: From mid July to lateSeptember.Comments: The stem has great quality,very stiff, supporting panicles well.Performed consistently well throughoutthe trial. A marvellous plant whichsupersedes ‘Grandiflora’. Slightly rounderpanicles than ‘Grandiflora’ with abeautiful yellow tip.

Hydrangea paniculata PINK DIAMOND‘Interhydia’

AGM (H4)1993

Habit: Upright and spreading,155 � 210cm.Stem: Red brown in full bloom tobrown after flowering.Panicle: Dense, broad, conical andtapered.Fertile floret: Buds green with pinktips, petals paler than 155A, becomingvery deep pink in autumn, antherscream, maturing to pale brown.Sterile floret: Paler than 151C,opening to 155A, flushing at margins,filling with red-purple 59C inautumn.Flowering: From late July to lateOctober.Comments: Known to be impressive butnot in trial having small panicles and agreater susceptibility to mineral deficiencythan others. Wonderful late colour, adeep glowing pink.

Hydrangea paniculata ‘Kyushu’

AGM (H4)1993

Habit: Upright and uneven,110 � 125cm.Foliage: Yellow green, slightly darkerthan 146A, glossy.Stem: Pale grey green 148D, greenerin leaf axils, lower wood pale brownafter flowering.Panicle: Open, narrow and tapered.Fertile floret: Buds greenish white,petals white.Sterile floret: Starting greenish yellow160D, becoming white 155A lightlytinged buff yellow. Only one sterilefloret per cluster.Flowering: From mid July to midSeptember.Comments: Flowers early. Good forsmall gardens. Very attractive to insectshaving more fertile flowers than manyothers. Responds well to hard pruning,producing the best panicles. Sells welland looks good in a pot. Sterile floretsremain white.

Hydrangea paniculata ‘Limelight’ PBR

AGM(H4)2008

Habit: Robust, upright and spreading,165 � 225cm.Foliage: Yellow green 146A.Stem: Pale grey green 148D, lightlyblushed pink in places, lower woodpale brown.Panicle: Very dense, broad, conicaland tapered.Fertile floret: Green buds.Sterile floret: Pale lime green, nearest150C, then grading through 150D towhite, some buds and floret bosseswith pink flush; lime green and pinkat season end.Flowering: From late mid July to earlyOctober 2008.Comments: Distinct and outstanding,stunning lime green flowers. Mediumpruning produces the best effect,otherwise large dense florets have a slighttendency to flop.

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Hydrangea paniculata ‘Silver Dollar’

AGM(H4)2008

Habit: Upright to moderatelyspreading, 125 � 165cm.Foliage: Yellow green, a little greenerthan 146A.Stem: White lenticels; lower stem andinflorescence axis flushed pink 187D;lower stem turning brown 200D duringand after flowering.Panicle: Very dense, broadly conical,and rounded.Fertile floret: Very few, cream in budthen white, perhaps one or two perterminal cluster but covered by themuch more numerous sterile florets.Sterile floret: Ranging from greyedyellow 160B-C to white, some olderflorets with pink tipped bosses,becoming pink flushed.Scent: Very slight fragrance.Flowering: from mid July to late Sept.Comments: Distinct compact habit andvery dense panicle. Sterile florets mature toa good pink. One of the most compactapart from ‘Dharuma’. Strong stemssupport heavy heads well. Responds wellto pruning, resulting in larger panicles anddelayed flowering thereby extending theflowering period. Good for small gardens.

Hydrangea paniculata ‘Unique’

AGM (H4)1993*

Habit: Upright to slightly sprawling,160 � 175cm.Foliage: Yellow green 146A, mostly inwhorls of 3.Stem: Pale grey green 148D, stronglyblushed pink in places, especially inlower inflorescence; lower woodreddish brown.Panicle: Dense, conical and tapered.Fertile floret: Buds pink 55C, flowerswhite, anthers pink-purple.Sterile floret: Pale lime green, nearest151C when immature, then gradingthrough 150D to white. Floret bossesand older florets with pink flush.Flowering: From late July to earlyOctober.Comments: Did not meet expectationsin trial. Much better, older plants can beseen on Battleston Hill where they havemore well-developed root systems andspace. Probably superseded by morerecent introductions.

Hydrangea paniculata ‘Pink Lady’

AGM subject to availability

Habit: Upright to arching,170 � 210cm.Foliage: Green 147A.Stem: Green in inflorescence, brown177C elsewhere in later season.Panicle: Half open to dense, long witha rounded top.Fertile floret: Cream bud with pink tip.Sterile floret: Cream maturing towhite, becoming flushed with pink57D at the end of the season.Flowering: From early July to earlyOctober 2008.Comments: Distinctive, attractive pinkflushing developing around the margin ofthe cream sterile florets, handsome broadleaf. Benefits from hard pruning, producinglarger panicles than unpruned plant.

Hydrangea paniculata PINKY-WINKY‘Dvppinky’ PBR

AGM(H4)2008

Habit: Nicely upright to lightlyspreading, compact, 140 � 160cm.Foliage: Yellow green, greener than146A, petioles flushed dark red.Stem: Strongly flushed deep purplishred 187C/D, maturing to brown175A/B.Panicle: Dense, conical and tapered.Fertile floret: Buds tipped pink, petalswhite.Sterile floret: Lime green 150C,maturing through greyed yellow 160Dto white with pink bosses, very deeppink at the end of the season.Scent: Spicy.Flowering: From early August to thefirst week of October.Comments: Very distinct, sturdy andupright. Good dark red stems and pinksterile florets at maturity, probably thedeepest pink. Responded well to pruning,displaying the perfect pruning-dependentflowering sequence from unpruned(earliest), to medium and hard pruned(latest). Suitable for small gardens.

RHS Plant Trials Bulletin8

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Selection table

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Panicle typesThe apparent density of the panicle depends on theratio of sterile to fertile flowers. Plants in the wildusually have inflorescences with many small, fertileflowers and relatively few sterile flowers, giving theflower heads a delicate appearance similar to a lace-cap.Many cultivated forms have a higher proportion ofsterile flowers, making the flower heads denser andshowier. The density of the panicle is one of the mostimportant ornamental characteristics of a cultivar and afeature that, along with the colour changes that maytake place as the panicle matures, helps to make itvisually distinctive. Our selection table assigns thepanicle density of each cultivar to one of four categories(open, half-open, dense and very dense), according tothe ratio of sterile to fertile flowers. This convention wasoriginally introduced during assessment of the DutchEuro-Trial.

Open <10% sterile flowers, >90% fertile flowerse.g. ‘Kyushu’

Half open >10% and <50% sterile flowers e.g. ‘Big Ben’

Dense >50% and <80% sterile flowers e.g. ‘Dolly’

Very dense >80% to 100% sterile flowerse.g. ‘Phantom’ and ‘Limelight’

‘Ammarin’

Compact habit, red stems, dense, bluntpanicles. Very distinctive, attractive,white sterile florets, pale pink later.Foliage scorch, reflecting sensitivity tomineral deficiency. Flowering from earlyAugust to late September. 150 � 165cm.

Raised and sent by Rein and Mark BulkNursery, 1999.

‘Big Ben’ ���

Half-open panicle. Outstanding,excellent red stems. Sterile florets go offreally well to pink. Ideal for the largergarden. Flowering from early August tomid October. 170 � 180cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland, 1990; sent byC R Sanders.

‘Bridal Veil’

An excellent flower arranger’s plant withhuge rounded, dense, blunt paniclesand unusual sterile florets withdistinctive serrated margins. Stamenshave comparatively long filaments. Planttends to flop badly. Better grown insome shade. Flowering from late June tolate August. 90 � 130cm.

Raised in 1975 and sent on behalf ofJ de Belder, Kalmthout Arboretum,Belgium. A seedling of ‘White Moth’.

‘Brussels Lace’ ��

Distinctive fine florets and half open,lacy, tapered panicles; compact habit,staying white in late season. Differentpruning regimes seem to have littleeffect. Flowering from late July to midSeptember. 120 � 160cm.

Raised in 1975 by R & J de Belder,Kalmthout Arboretum, Belgium;supplied by RHS Wisley. A seedling of‘Unique’.

Comparison with other TrialsReports from the Dutch and French Eurotrials indicatethat ‘Big Ben’, ‘Limelight’ and ‘Phantom’ were three ofthe top four performers in both trials. The other topperformers in these trials were PINK-WINKY ‘Dvppinky’and ‘Mega Pearl’. Of these, only ‘Mega Pearl’ did notreceive the AGM in the Wisley trial.

Nomenclatural notes‘Burgundy Lace’There was found to be confusion over the identity of‘Burgundy Lace’. Plants from two sources entered as‘Burgundy Lace’ were identified as PINK DIAMOND

‘Interhydia’, while one that most likely was ‘BurgundyLace’ had been entered as ‘Brussels Lace’. A plant enteredas ‘Burgundy Lace’ Compact Form was found to beindistinguishable from PINK DIAMOND. The flower heads ofPINK DIAMOND turn a deeper pink than those of ‘BurgundyLace’.

‘Webb’s’‘Webb’s’, originally known as ‘Webb’s Variety’, was notconsidered to be distinct from ‘Grandiflora’.

‘Tardiva’Plants from two sources entered as ‘Tardiva’ were notedto be very similar to ‘Floribunda’, although their trueidentity could not be established. They did not differsignificantly in their panicle characteristics or floweringtime.

DART’S LITTLE DOT ‘Darlido’Two entries of DART’S LITTLE DOT ‘Darlido’ turned out tobe ‘Harry’s Souvenir’, suggesting that they may havebecome confused in the trade.

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Selection table

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‘Burgundy Lace’

Flowering from early August to earlyOctober. Open panicle, pink flushedfertile floret buds, sterile floret lightlyflushed with pink as it ages, particularlyat margins and veins. No differentialeffects of pruning demonstrated, allplants and panicles an even size. 140 �150cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1975, suppliedby the Crown Estate Commissioners.

See nomenclatural notes.

‘Chantilly Lace’ ��

Good habit and clear white floretsageing to pink on a half open to densepanicle. Very free flowering, elegant,light and pretty. One plant died fromthe effects of honey fungus. Floweringfrom early August to late September.140 � 170cm.

A seedling of ‘Tardiva’ sent by MichaelDirr, selected by Kay Bowman andM Dirr, USA.

DART’S LITTLE DOT ‘Darlido’ PBR �

Most dwarf of all the entries, openpanicle flowering for a long period, lateJuly to late September. Holds flowers upwell and doesn’t need pruning. Goodfront of border plant. Flowering fromlate July to early October. 45 � 105cm.

Introduced pre 1995 by DarthuizerNurseries. Sent by the raiser.

See nomenclatural notes.

‘Dharuma’ ��

Attractive red stems, early and freeflowering, open to half open panicles,compact, bold foliage. Deep pink sterileflorets and fruits at maturity. Slower todevelop than most, excellent for the smallgarden. Best left entirely unpruned, it willnaturally reach 1 to 1½m. Flowering frommid June to early October. 120 � 115cm.

Imported from Japan, 1989, sent by Reinand Mark Bulk Nursery and C R Sanders.Believed to be H. paniculata �H. heteromalla resulting in the flattenedinflorescence.

‘Dolly’ ���

Creamy florets gradually develop somepink in dense panicles resembling‘Grandiflora’. Responds well to pruning.Medium pruning is thought preferableas hard pruning produces very large,heavy heads which tend to flop.165 � 160cm. Flowering from late Julyto late September.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland, 1990; supplied byRHS Wisley.

AGM subject to availability.

EARLY SENSATION ‘Bulk’ PBR ��

Excellent foliage and red stems,vigorous. A good succession of dense tohalf open, rounded panicles similar tothose of ‘Dharuma,‘ providing a longlasting display, becoming very deeppink. Would make an excellent hedge.Flowering from mid June to earlyOctober. 145 � 200cm.

Raised c.2004, sent by Rein and Mark BulkNursery; ‘Dharuma’ � PINK DIAMOND.Known as QUICKFIRE in the USA.

‘Everest’

Half open panicle, not considered verydistinct and a dirty pink as flowers goover. Flowering from mid July to earlySeptember. Improved by hard pruningresulting in better sized panicles.160 � 190cm.

Raised at the Sir Harold Hillier Gardens& Arboretum 1989, supplied by RHSWisley and Crown Estate Commissioners.

‘Floribunda’*

Elegant, pointed panicles, creamy floretsdevelop some pink as they age. Requirespruning to prevent it from becomingtoo large. Flowering from late July toearly September. 190 � 210cms.

Introduced by Carl J Maximowicz fromJapan to Botanic Gardens ofSt Petersburg in 1890; distributedthroughout Europe by R & J de Belder,Kalmthout Arboretum, Belgium.Supplied by RHS Wisley and the CrownEstate Commissioners.

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11Hydrangea paniculata

Hydrangea paniculata �

from Taiwan

Floriferous, distinctly subtle and dainty,open panicles. Combines well withherbaceous plants and is fantastic forbutterflies. A good flower arranger’splant with attractive red stems.Flowering from mid July to late August.200 � 180cm.

One of a number of introductions fromTaiwan by Bleddyn Wynn-Jones, CrûgFarm Plants; sent by Rein and Mark BulkNursery.

‘Kyushu’ ���

Very attractive to insects as it has morefertile florets than many other cultivars.Open panicle, sterile florets are small andremain white. Compact, suiting a smallgarden but superseded by recentintroductions. Does well in a pot.Responds well to hard pruning producingattractive panicles. Flowering from midJuly to mid September. 110 � 125cm.

Introduced by Collingwood Ingramfrom Kyushu, Japan; distributed throughEurope by R & J de Belder, KalmthoutArboretum, Belgium; sent by the CrownEstate Commissioners.

‘Limelight’ PBR ���

Stunning and very distinctive, verydense, lime green panicles ageingthrough cream to pink. Excellent glossyfoliage. Medium pruning isrecommended, reducing flopping ofheavy panicles. Flowering from mid Julyto early October. 165 � 225cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland in 1990; sent by RHSWisley.

‘Last Post’ ��

Compact habit, ideal for the smallergarden. Very pretty, beautifully shapedsterile florets with attractively reflexedsepals on half open panicles which ageto pink. Fertile florets pink in bud. Goodred stems. Responds well and improvedby pruning. Flowering from mid July toearly October. 110 � 200cm.

Introduced in 1999 by DarthuizerNurseries. Sent by the raiser.

‘Grandiflora’*

Dense panicles cause stems to flop.Superseded by ‘Phantom’. It is betternot to prune so as to reduce vigour,panicle size and the tendency to flop.Flowering from the end of August to theend of September. 100 � 130cm.Widely grown in the USA and known asthe PG or pee gee hydrangea.

Introduced by Philipp von Siebold in1862 from Japan; sent by the CrownEstate Commissioners.

‘Great Escape’

Tall bush with sturdy branches, narrow,open panicles. No pinking of the sterileflorets. Flowering from mid July to lateAugust. 185 � 205cm.

Introduced pre 1995 by DarthuizerNurseries. Sent by the raiser.

‘Greenspire’ �

Vigorous, open to half open panicle.There are many of this style. No pink atmaturity. Flowering from late July to lateSeptember. 200 � 220cm.

Raised by R & J de Belder, 1975, aseedling of ‘Unique’. Supplied by RHSWisley and the Crown EstateCommissioners.

‘Harry’s Souvenir’

All nine plants of this cultivar failed tosurvive the trial. Low growing, verydense panicles. Arching flowering stemstended to flop. Bright green anthers.

Raised by the Research Station forNursery Production, Boskoop, Holland;named in memory of Harry van de Laar.Sent by Rein and Mark Bulk Nursery andWard van Teylingen.

Height and SpreadMeasurements for heightand spread relate to theunpruned, approximatelyfour year old plant ofeach entry.

Performance rating:The judging scores aresummarised by aperformance rating from0 – 3 stars.

��� Excellent

�� Very good

� Good

none Average to poor,or not judged

Early season

Mid-season

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* Recommended to berescinded at the AGMReview in 2012

Selection table

RHS Plant Trials Bulletin12

‘National Arboretum’

A tall sprawling shrub with brown stemsand open panicles. Sterile florets ageingto pale pink. Flowering from mid July tolate September. 140 � 170cm.

Raised by Pieter Zwijnenburg Jr.,Boskoop, Holland; sent by RHS Wisley.

‘October Bride’

Upright to lightly spreading habit andopen panicle. Flowering from late July tomid October, until the first frosts.195 � 225cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1967; a seedlingof ‘Tardiva’; sent by Derby City ParksDepartment.

‘Papillon’

Poor, sprawling habit. Open to halfopen panicle. ‘Papillon‘, the Frenchword for butterfly, is said to describe theshape of the sterile florets, however thiswas not obvious in trial. Flowering fromearly August to mid September.160 � 210cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1970; sent byRein and Mark Bulk Nursery.

‘Pee Wee’

Described as very unique and compactform of the pee gee Hydrangea,‘Grandiflora’, but it was not impressivein trial. The pruning regime resulted inbig differences between the threeplants; the back plant was rather gappy,the medium pruned less so with lots ofnew growth and the unpruned plant thebest. However, the dense panicles onthe hard pruned plant went on to flop.Flowering from mid July to earlyOctober. 175 � 185cm.

Raiser unknown, sent by Rein and MarkBulk Nursery.

‘Martinvast’ ��

Attractive sterile florets with serratedmargins on half open paniclesbecoming lightly flushed with pink inmaturity. Compact and free flowering,good foliage. Flowering from mid July tolate September. 110 � 135cm .

Introduced by J de Belder, named afterthe Parc de Martinvaast, Cherbourg,France; sent by R Mallet.

‘Mega Pearl’ �

Pearly sterile florets but rather an openhabit and crowded, half open panicle.Evidence of foliage scorch. Floweringfrom late July to early October.135 � 150cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland in 1990; supplied byRHS Wisley.

‘Mid Late Summer’ �

Good sturdy plant, very floriferous butcrowded, half open panicle goes off topink and ages gracefully. Not as good as‘Big Ben’ and similar to ‘Mega Pearl’.Flowering from mid July to earlyOctober. 200 � 205cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland in 1990; sent by RHSWisley.

‘Mustila‘

Poor habit and rather thin, attractive redstems. Early, half open panicles.Flowering from late June to lateSeptember. 125 � 100cm.

Sent by the Research Station, Boskoop,Holland, named in 1998 after theArboretum Mustila near Elimäki in SouthFinland founded by A F Tigerstedt in1902.

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13Hydrangea paniculata

‘Praecox’ ��

A very distinctive flower and lime greenearly foliage, having substantial impactparticularly when unpruned. Freeflowering and tough. Broad, half openpanicle with elongated, ovate, sterileflorets. Excellent edge of woodland plantthat can make a very large specimen.Flowering from late June to mid August;the first to flower. 140� 155cm.

Wild collected in Japan by C S Sargent,founder of the Arnold Arboretum, USA.

‘Sherwood’ �

Attractive, cupped sterile florets on openpanicles. Makes a big mound withpotential to sprawl. Flowering from lateJune to late September. 165 � 185cm.

Raised and sent by Sherwood CottageNursery.

‘Silver Dollar’ ���

Compact habit and very dense panicles.Sterile florets mature to a good pink.One of the most compact apart from‘Dharuma’. Strong stems support heavyheads well. Responds well to pruning,resulting in larger panicles and delayedflowering thereby extending theflowering period. Good for smallgardens. Flowering from mid July to lateSeptember. 125 � 165cm.

Raised by Pieter Zwijnenburg Jr, Boskoop,Holland in 1990; supplied by RHS Wisley.

‘Skylight’ ��

Excellent half open panicles of verygood quality, clean, white florets.Demonstrating the greatest differencebetween the 3 plants, the unprunedplant flowering significantly earlier, farahead of the medium and hard prunedplants where flowering extends into lateOctober. Flowering from mid July toearly October. 165 � 230cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland in 1990; supplied byRHS Wisley.

‘Phantom’ ���

One of the most impressive entries. Thestem has great quality, very stiff,supporting the very dense panicles well.Slightly rounder panicles than‘Grandiflora’ with a beautiful yellow tip,denser than ‘Limelight’. It performedconsistently well throughout the trial, amarvellous plant superseding‘Grandiflora’. Flowering from mid July tolate September. 145 � 195cm.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland in 1990; sent byC Lane, C R Sanders and RHS Wisley.

PINK DIAMOND ‘Interhydia’ ���

This plant showed sensitivity to anapparent mineral deficiency on the trialsite, yet is known to perform well,without leaf scorch, elsewhere. The lateseason colour was magnificent, the densepanicles developing a deep, glowing pinkwhich made the plants stand out fromthose around them. Flowering from lateJuly to late October. 155 � 210cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1980; suppliedby RHS Wisley and the Crown EstateCommissioners.

‘Pink Lady’ ���

Distinctive, attractive pink flushingdeveloping around the margin of thecream sterile floret. Half open to densepanicle, handsome broad leaf. Benefitsfrom hard pruning, producing largerpanicles than the unpruned plant.Flowering from early July to earlyOctober. 170 � 210cm.

Raised by Pieter Zwijnenburg Jr, Boskoop,Holland in 1990; sent by C R Sanders andRHS Wisley.

AGM subject to availability.

PINKY-WINKY ‘Dvppinky’ ���

Very distinct, sturdy upright and compact.Good dark red stems and pink sterileflorets at maturity, probably the deepestpink. Responded well to pruning,displaying the perfect pruning-dependentflowering sequence from unpruned tohard pruned. Suitable for small gardens.Flowering from the middle of July to thefirst week of October. 140 � 160cm.

Raised at the Research Station Melle,Belgium, 2003; sent by C R Sanders.

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Height and SpreadMeasurements for heightand spread relate to theunpruned, approximatelyfour year old plant ofeach entry.

Performance rating:The judging scores aresummarised by aperformance rating from0 – 3 stars.

��� Excellent

�� Very good

� Good

none Average to poor,or not judged

Early season

Mid-season

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RHS Plant Trials Bulletin14

VANILLE-FRAISE ‘Renhy’® ��

Low, spreading shrub. The best redstem, but an inherent weakness resultedin very dense panicles flopping, the hardpruned plant holding up best. Appearedto be less weatherproof than many,resulting in early browning of theotherwise wonderful, pink, maturesterile florets. 125 � 185cm. Floweringfrom mid July to early October.

Bred by Eric Renault, Pépinières Renault,Gorron, France. Sent by SAPHO.

‘Vera’ �

‘Brussels Lace’ type, drab foliage, similarto the wild type. The name probablycomes from the Latin word vera,meaning truth, plants were oftendescribed as var. ‘vera’ in the past but itis not in general use now. Open to halfopen panicle, flowering from mid July toearly September. 140 � 155cm.

Raised by de Kort, who preceded the deBelders at Kalmthout Arboretum. Sentby Derby City Parks Department.

‘Webb’s’

Flowering from the beginning of Augustto early October. 135 � 195cm.

Raised by J A Webb, Huntsville,Alabama, USA in 2003. Sent by Rein andMark Bulk Nursery and RHS Wisley exP Zwijnenburg Jr.

See nomenclatural notes.

‘White Goliath’

syn. ‘Goliath’

Named for its vigour but is no morevigorous than and is similar to manyothers. A medium, upright, spreadingplant with narrow, open panicles, floretsflushing pale pink with age. Floweringfrom mid July to mid September.170 � 170cm.

A chance seedling at Rein and Mark BulkNursery, 2000; sent by the raiser.

STARLIGHT FANTASY ‘Degustar’ ��

Distinctive sterile floret on half open todense panicle. Sinuate leaf and healthy,glossy foliage. Late flowering, floretsmaturing to light pink. Flowering frommid July to early October. 120 � 130 cm.

Raised by Frères de Gussem, Belgium,PBR applied for. Known in France as‘Perle d’Automne’; sent by M Foster.

‘Tardiva’

Flowering from late July to earlyOctober. 135 � 130cm

Sent by the Crown Estate Commissionersand RHS Wisley.

See nomenclatural notes.

‘Tender Rose’ �

A half open panicle, initially displaying anice contrast between pink fertile budsand white sterile florets which mature toan unremarkable pale pink. Pruning hasno marked effect. Flowering from midJuly to late September. 115 � 120cm.

Raised by Darthuizer Nurseries before1995, selected as a seedling from‘Kyushu’. Sent by Darthuizer Nurseries.

‘Unique’* ��

This cultivar did not meet expectationsin trial, although much better, olderplants can be seen on Battleston Hill,RHS Wisley Garden. Superseded bymore recent introductions. Densepanicles, flowering from late July to earlyOctober. 160 � 175cm.

The first introduction of R & J de Belderpre 1970 as a seedling from‘Floribunda’. Sent by the Crown EstateCommissioners and RHS Wisley.

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Height and SpreadMeasurements for heightand spread relate to theunpruned, approximatelyfour year old plant ofeach entry.

Performance rating:The judging scores aresummarised by aperformance rating from0 – 3 stars.

��� Excellent

�� Very good

� Good

none Average to poor,or not judged

Early season

Mid-season

Late seasonL

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Woody Plant Trials Sub-committeeChairman: Chris SandersVice-Chairman: John Hillier

Chris Brickell Peter CattDavid Clark Maurice FosterJohn Gallagher Kevin HughesRoy Lancaster Michael HicksonJohn Humphris Chris LaneDavid Masters Harvey Stephens

Suppliers of Plants to the TrialJelena de Belder (deceased), Hemelrijk, Essen, Belgium.Rein and Mark Bulk Nursery, Rijneveld 115, 2771 XV

Boskoop, The Netherlands.Crown Estate Commissioners, The Great Park, Windsor,

Berkshire SL4 2HT.Darthuizer Boomkwekerijen Bv, Broekweg 3, 3956 NE

Leersum, The Netherlands.Derby City Parks Dept, Celtic House, Heritage Gate,

Friary Street, Derby DE1 1QX.M Dirr, Georgia, USAM Foster, KentCollection d’Hydrangea Shamrock, Route de l’Eglise76119

Varengeville sur Mer, France.Chris Lane, Witch Hazel Nursery, Callways Lane,

Newington, Sittingbourne, Kent ME9 7LU.RHS Garden Wisley, Woking, Surrey GU23 6QBC R Sanders, StaffordshireSAPHO, Les Islettes, 49250, La Menitre, FranceSherwood Cottage Nursery, Sherwood Cottage,

Newton St Cyres, Exeter EX5 5BT.Ward van Teylingen, Goudse Rijweg 326, 2771 BA

Boskoop, The Netherlands.

National Collections of HydrangeaMr P R Smith, Derby City Parks, 15 Stores Road , Derby,

Derbyshire, DE21 4BD. Tel: 01332 641560Mrs S Newman, The Lakeland Horticultural Society

Garden at Holehird, Patterdale Road, Windermere,Cumbria, LA23 1NP. Tel:01539 446008

Mr S Wingett, The Garden House, Erbistock, Wrexham,LL13 0DL. Tel: 01978 781149

Further reading:Church, G. 1999. Hydrangeas. Cassell.Dirr, M.A. 2004. Hydrangeas for American Gardens. Timber

Press.Haworth-Booth, M. 1984. The Hydrangeas (5th ed.)

Constable.Lawson-Hall, T. and Rothera, B. 1995 Hydrangeas A

Garden Guide. B.T. Batsford.Mallet, C. 2008. Hortensienatlas. 2008. Ulmer.Van Gelderen, C.J. and Van Gelderen, D.M. 2004.

Encyclopedia of Hydrangeas. Timber Press.

15Hydrangea paniculata

‘White Lace’

Not outstanding or distinctive, only1 plant of 6 survived the trial. Openpanicle, flowering from late June tolate August. 130 � 185cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1970; sent byC R Sanders and RHS Wisley.

‘White Lady’

Not represented in the RHS trial, Euro-trial only. Attractive serrate, sterilefloret petals. Half open panicles.

Raised by Pieter Zwijnenburg Jr,Boskoop, Holland, 1990.

‘White Moth’ �

Recommended to be grown in a largegarden as a specimen shrub, takingtime to reach its full potential.Excellent for shade, it glows in reducedlight. Half open, rounded panicles.Pruning produces larger blooms with atendency to flop, so better simplydeadheaded. Flowering from late Juneto late August. 195 � 190cm.

Raised by R & J de Belder, KalmthoutArboretum, Belgium in 1975, suppliedby RHS Wisley.

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For contact details of nurseries that can supply plants seeRHS Plant Finder, also available online at:www.rhs.org.uk/rhsplantfinder/plantfinder.asp

RHS Plant TrialsWith so many different types of gardener and so manydifferent cultivars available to them in each group ofplants, it is important that a system of recommendation isin place to help with selection at point of sale. Theserecommendations must be clear and reliable to ensure thatof the thousands of plants available in the UK, aproportion are known to be excellent garden plants. TheRHS provides this information through its extensiveprogramme of plant trials held at RHS gardens in the UK.The RHS Award of Garden Merit signifies the selectionof the best cultivars for general garden use.

RHS plant trials serve the professional gardener who wantsto know the range of plants available, including the latestbreeding and selection programmes, with their distinctivecharacteristics and provenance. They also serve theamateur who wants to know which plants will grow andperform well in a particular garden situation.

The RHS has an unrivalled resource of knowledge andexpertise and is therefore best placed to conduct planttrials for the UK gardening market.

RHS Trials BulletinsBegonia Rex Cultorum Group: Number 16Canna: Number 3Chilli Peppers: Number 22Clematis alpina & C. macropetala: Number 21Daisies (yellow perennial): Number 6Delphinium: Number 5Fuchsia (hardy): Number 12Geranium (hardy) Stage 1: Number 10Geranium (hardy) Stage 2: Number 14Geranium (hardy) Stage 3: Number 18Hyacinthaceae (little blue bulbs): Number 11Hydrangea paniculata: Number 23Iris (bearded): Number 17Lavenders (hardy): Number 2Miscanthus: Number 7Peppers (sweet): Number 15Potatoes (salad): Number 8Potentilla (shrubby): Number 1Rhododendron yakushimanum and hybrids: Number 13Runner Beans: Number 19Saxifrages (silver): Number 9Sedums (herbaceous): Number 20Spiraea japonica (with coloured leaves): Number 4

These bulletins can be viewed at a larger size on theRHS Website: www.rhs.org.ukplants/trials_bulletins.asp

RHS Plant Trials and AssessmentsOnline publications, to complement the RHS PlantTrials Bulletins series

Caryopteris: Number 2Perovskia: Number 3Pittosporum tenuifolium hybrids and cultivars: Number 1

Trials indexes can be obtained from The Trials Office,RHS Garden Wisley, Woking, Surrey GU23 6QB,Email: [email protected] reports on the web atwww.rhs.org.uk/plants/award_plants.asp

The Royal Horticultural SocietyThe RHS is the UK’s leading gardening charity dedicated toadvancing horticulture and promoting good gardening. Itscharitable work includes providing expert advice andinformation, advancing horticulture, training the nextgeneration of gardeners, helping school children learnabout plants, and conducting research into plants, pestsand environmental issues affecting gardeners. The RHSAGM plant trial scheme is an important part of this work.

The RHS receives no government grants and for everypound received from members’ subscriptions we need toraise more than twice as much again to fund our charitablework. We also rely on donations and sponsorship tosupplement income from our garden operations, flowershows, shops and plant centres.

RHS HerbariumThe RHS Herbarium keeps a record of trial cultivars as driedspecimens with detailed descriptions and photographicimages. This forms an important reference for thehorticultural industry. Any new cultivars are highlightedand a nomenclatural standard specimen is preserved anddescribed.

The RHS Herbarium, stored at RHS Garden Wisley, is thelargest active horticultural herbarium in the world. Atpresent the collection contains about 80,000 herbariumspecimens and over 40,000 images of plants. Material isactively collected from a wide spectrum of sourcesincluding RHS plant trials.

The RHS, the UK’s leading gardening charity

RHS Garden, WisleyWokingSurreyGU23 6QBe-mail: [email protected]

www.rhs.org.uk/trials

Reg charity no. 222879in Scotland SCO38262

All text and images Copyright RHS 2008 except whereotherwise stated.

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