Sully, what are you trying to accomplish? Are you seeking to add a lemon flavor background to your Blackberry wine? If so, I would use either the zest of the lemon and not the whole lemon peel or I would use a few drops of pure lemon extract (mixture of lemon oil and alcohol). Be careful with the lemon extract bcause a little goes a long way. Bench test with about a quart of wine starting with a single drop and then scale it up. I am sorry I can't help with the lemon grass. I know what it is and have used it in Thai cooking. It just has a lemon flavor and is not related to the citrus fruit.
Edit: Just did some reading on lemon grass and it is more interesting than I thought. It seems in has both preservative and anti-fungal properties Since it is used as a flavoring in food, I suppose that it could be used. In that it is also a pesticide, I don't think I am adventurous enough to try it.