▁another ▁plant ▁which ▁should ▁never ▁be ▁handled ▁as ▁the ▁sap ▁can ▁cause ▁severe ▁bl ister ing ▁and ▁sc arring ▁of ▁the ▁skin . ▁A yr shire ▁R ivers ▁Trust ▁are ▁a ▁local ▁conservation ▁char ity ▁that ▁have ▁been ▁highly ▁effective ▁cont rolling ▁invas ive ▁we eds ▁in ▁A yr shire ▁and ▁are ▁soon ▁to ▁tack le ▁Gi ant ▁Hog we ed ▁on ▁the ▁Gar no ck ▁and ▁other ▁rivers ▁in ▁North ▁A yr shire . ▁More ▁information ▁on ▁the ▁work ▁of ▁the ▁Trust ▁is ▁available ▁through ▁their ▁website ▁at ▁www . ay r sh ir er iver str ust . org ▁▁▁ ▁The ▁Stewart on ▁F lower ▁or ▁p ink ▁purs lane ▁( Cl ay ton ia ▁sib ir ica ) ▁is ▁common ▁in ▁wet ter ▁areas . ▁It ▁has ▁white ▁or ▁p ink ▁flowers ▁at ▁this ▁site , ▁but ▁closer ▁to ▁Stewart on ▁it ▁is ▁almost ▁always ▁white . ▁It ▁seems ▁that ▁it ▁was ▁first ▁introduced ▁as ▁a ▁white ▁variety ▁in ▁the ▁Stewart on ▁area ▁in ▁Victor ian ▁times ▁and ▁the ▁common ▁p ink ▁variety , ▁introduced ▁later , ▁spread ▁to ▁other ▁areas . ▁Dal gar ven , ▁it ▁seems , ▁is ▁on ▁the ▁edge ▁of ▁the ▁white ▁flower ▁zone ▁of ▁domin ance . ▁Dal gar ven ▁is ▁the ▁only ▁known ▁site ▁for ▁the ▁P ocket ▁Pl um ▁gall ▁T ap hr ina ▁p adi ▁which ▁develop s ▁on ▁Bird ▁Cher ry . ▁ ▁Co pp icing ▁of ▁the ▁rivers ide ▁al der ▁trees ▁is ▁still ▁carried ▁out . ▁Ald ers ▁grow