▁cm ▁long ▁by ▁ 3 ▁– ▁ 5 ▁cm ▁wide , ▁are ▁lance olate ▁or ▁narrow ly ▁ob ov ate , ▁ac uminate ▁at ▁the ▁tip ▁and ▁with ▁a ▁c une ate ▁base , ▁light ▁green ▁in ▁colour , ▁turning ▁a ▁deep ▁yellow ▁( s ometimes ▁following ▁a ▁brief ▁orange - red ) ▁in ▁aut umn . ▁The ▁sam ara ▁is ▁heart - sh aped , ▁with ▁marg inal ▁seed ▁by ▁a ▁marked ly ▁open ▁not ch . ▁ ▁P ests ▁and ▁dise ases ▁' H o ers hol mi ensis ' ▁is ▁sus cept ible ▁to ▁Dutch ▁el m ▁disease ▁and ▁Cor al - spot ▁F ung us ▁N ect ria ▁c inn ab arina . ▁ ▁Cult iv ation ▁The ▁tree ▁is ▁cultiv ated ▁in ▁Den mark , ▁Sweden , ▁Finland , ▁and ▁the ▁Netherlands . ▁In ▁Den mark ▁it ▁is ▁usually ▁propag ated ▁by ▁base - gra ft ing ▁on ▁w ych ▁el m . ▁Here ▁the ▁oldest ▁known ▁plant ation ▁was ▁ 6 5 ▁trees ▁on ▁the ▁T ub org ve j , ▁C open hagen , ▁plant ed ▁in ▁ 1 9 0 6 . ▁The ▁Sp ä th ▁nur ser y ▁of ▁Berlin ▁distributed ▁' H o ers hol mi ensis ' ▁from ▁the ▁late ▁ 1 9 2 0 s . ▁In ▁the ▁Netherlands ▁it ▁was ▁plant ed ▁not ably ▁along ▁the ▁West lands gra cht ▁in ▁Amsterdam ▁where ▁it ▁still ▁surv ives , ▁although ▁upper ▁branches ▁are ▁often ▁killed ▁by ▁Cor al - spot ▁F