Hi thanks for your question. My name is ***** ***** I can help with this.
This will be a matter of construsing the deeds and the terms of the restriction, but I would imagine that it's a pretty simple case of the whole objective meaning of the clause being that the neighbour cannot interfere with the dividing hedge that stands between the two properties, irrespective of whether it's the same hedge or not.
I suppose, if you follow the logic here, bushes grow, and re-grow and change and even if the initial hedge does not die, what it present in 10 years time is not actually the same hedge, it is a grown version of what once was. The only difference in your case is that you've changed the actual thing, which was changing anyway though it being alive etc., and as such, I would imagine that it makes no difference to the covenant you're referring to.