▁seed less , ▁except ▁in ▁an ▁occas ional ▁large ▁ber ry . ▁When ▁d ried , ▁the ▁ra is ins ▁we igh ▁ ▁and ▁are ▁dark ▁brown ▁or ▁black . ▁Le aves ▁are ▁medium - s ized , ▁heart - sh aped , ▁and ▁ob long . ▁They ▁are ▁five - lob ed ▁with ▁deep ▁sin uses . ▁ ▁Cult iv ation ▁ ▁To ▁yield ▁sufficient ▁fruit , ▁Black ▁Cor inth ▁g rap es ▁need ▁to ▁be ▁carefully ▁managed . ▁ ▁In ▁ancient ▁times , ▁g ird ling ▁was ▁a ▁standard ▁practice ▁to ▁increase ▁the ▁set ▁and ▁size ▁of ▁seed less ▁g rap es , ▁until ▁the ▁discovery ▁of ▁the ▁plant ▁h orm one ▁g ib ber el lic ▁acid , ▁and ▁its ▁ability ▁to ▁do ▁the ▁same ▁thing ▁with ▁less ▁labor . ▁Histor ically , ▁Black ▁Cor inth ▁stock ▁was ▁probably ▁kept ▁for ▁its ▁pol len - produ cing ▁ab ilities , ▁so ▁other ▁female ▁flow ered ▁vari eties ▁( with ▁naturally ▁higher ▁yields ) ▁would ▁set ▁full ▁cro ps . ▁ ▁The ▁Black ▁Cor inth ▁cultiv ar ▁is ▁also ▁re put ed ▁to ▁be ▁very ▁pr one ▁to ▁pow der y ▁mil de w , ▁and ▁is ▁sus cept ible ▁to ▁numerous ▁other ▁dise ases ▁such ▁as ▁down y ▁mil de w ▁and ▁black ▁rot . ▁ ▁Greece ▁is ▁still ▁the ▁primary ▁producer ▁of ▁curr ants , ▁amount ing ▁to ▁about ▁ 8 0 % ▁of ▁total ▁world ▁production , ▁with ▁California , ▁South ▁Africa ▁and ▁Australia ▁sharing ▁most ▁of ▁the