ba . ▁It ▁is ▁a ▁very ▁vig orous ▁tree ▁with ▁marked ▁hy brid ▁vig our , ▁reaching ▁ 4 0   m ▁tall ▁and ▁with ▁a ▁tr unk ▁diameter ▁over ▁ 1 . 5   m ▁– ▁much ▁larger ▁than ▁either ▁of ▁its ▁parents . ▁Most ▁trees ▁in ▁cultiv ation ▁are ▁male , ▁but ▁female ▁trees ▁occur ▁naturally ▁and ▁some ▁of ▁these ▁are ▁also ▁propag ated . ▁ ▁Tax onomy ▁ ▁In ▁ 1 7 8 9 ▁William ▁A it on ▁described ▁the ▁grey ▁pop lar ▁as ▁a ▁variety ▁of ▁Pop ulus ▁al ba , ▁P .   al ba ▁var . ▁can esc ens . ▁In ▁ 1 8 0 4 , ▁James ▁Edward ▁Smith ▁raised ▁it ▁to ▁a ▁full ▁species , ▁Pop ulus ▁can esc ens . ▁He ▁described ▁differences ▁between ▁the ▁leaves ▁of ▁the ▁two ▁tax a : ▁P . ▁al ba ▁has ▁lo bed ▁leaves ▁with ▁snow - white ▁(" n ive us ") ▁unders ides , ▁whereas ▁P . ▁can esc ens ▁has ▁w avy - ed ged ▁leaves ▁with ▁ho ary ▁(" in can us ") ▁unders ides . ▁Later ▁authors ▁sometimes ▁noted ▁the ▁possibility ▁that ▁the ▁grey ▁pop lar ▁was ▁a ▁hy brid . ▁It ▁is ▁now ▁considered ▁to ▁be ▁a ▁hy brid ▁between ▁Pop ulus ▁al ba ▁and ▁Pop ulus ▁trem ula , ▁so ▁the ▁scientific ▁name ▁is ▁written ▁with ▁the ▁hy brid ▁symbol . ▁ ▁References ▁ ▁can esc ens ▁Category : Pl ant ▁not hos pecies <0x0A> </s> ▁The ▁G last on bury