so i have to get it from him?
yes go directley to Raminus to be sent to the count and after sent to a women where you will need 5 empty grand soul gems to continue with the quest, but like i said before be sure you havent closed all of the oblivion gates as you will not be able to hand over the blood grass.
That happend to me and now i am a perminant vampire, if anyone knows any alternative way of cureing vamperisim i will be glad to hear it just PM me.