Whatseemedlikea goodideawhen
a localcommunitygroupaskedmelast
summerif I fancieda spotof‘balsam-
bashing’soonfeltlikeanimpossibletask
onceI wasstandingamidstacresofthe
stuff,seriouslycontemplatinguprooting
it allbyhand.Theclosertowaterit is,the
biggerbalsamseemstogrow.Takeholdof
itsthick,fleshystem,giveit a sharppull
andit comesupeasilyenough– those
shallowrootsdon’tputupmuchofa fight.
Butit is thoseveryshallowrootsthatcan
causesucha probleminriverinehabitats.
Theyfailtobindtheriverbanks,which
makesthebaresoilpronetoerosionin
winterspates,whentheplantdiesback.Himalayanbalsamhasbeenreleased
manytimesacrosstheUKsinceitsarrival
inthelate1800s,notleastbybeekeepers
asa sourceofnectar.It producesmore
nectarperflowerthananyofournative
species,leadingsomeecologiststobelieve
thatitspresenceis preventingbeesfrom
pollinatingthenativeflora.
Plantsoftenevolvea strategyof
‘dispersalbyanimal’.TheHimalayan
balsam’sstrategycouldeasilybe
‘dispersalbychildren’,asfewcanresist
squeezingtheseedcapsuleonautumn
woodlandwalks,asit temptinglybulges
likea coiledspringbeforefiringits
cargowitha dramatic‘pop.’It’san
impressivemechanism,shooting
theseedsupto7m.Shouldthey
landina river,theseedsare
carrieddownstreamandcansoon
populatethewholecatchment.Insidethosedelicatebloomsthuslies
theblueprintfora ruthlesscompetitor.
Someofthesespeciesarefamiliar
tousall.Japaneseknotweedandgiant
hogweedarecommonsightsonrecently
disturbedground,takingoverrailway
embankmentsandriverbanks,particularly
inurbansettings.Theyareoftenfound
jockeyingforpositionwitha thirdinvader- Himalayanbalsam.Betweenthem,they
aresmotheringournativeplantlife.
A longwayfromhome
Initshomerangeinthefoothillsofthe
Himalayas,Himalayanbalsamgrows
insmallclusters.Withitsdelicate,pink,
orchid-likeblooms,it is easytoseewhy
it appealedtothoseintrepidcollectors.
Butindensestandsthatcanengulf
acresofriverbank,it moreresembles
anexplosionina confettifactory.SabenaJane
Backb
rd/A
amyAugust 2020 BBC Wildlife 33
NEWS FEATURE