| Yes, there were threads on them before - they are random and they start opening up everywhere once you do the Kvatch Gate for the Main Quest. Do not close that one before it pops up as a quest. Once you've done it, you'll be drowning in the Gates.
But you can get bloodgrass in the shops as well, for that you can do a search here as to where. Anvil, the docks I think is the place, but do a search on it.
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And He whispered to me in the darkness as we lay together, Tell Me where to touch you so that I can drive you insane; tell Me where to touch you to give you ultimate pleasure, tell Me where to touch you so that we will truly own each other. And I kissed Him softly and whispered back, Touch my mind. | 
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