Posted: 09/06/2016 at 12:21
I would complain to the council. Emphasise that if the hedge dies, you will want it replacing with another of equal size and type. That should put the wind up them. I have a buddleja growing in front of the front wall, and bulbs, and the council know not to spray there, when they go round spraying the bus stops, manhole covers etc. They sprayed it one year, I made such a fuss they have never done it since.
Hawthorn hedges are pretty bombproof once established, which that is, dryness and frosts wont touch them. The soil will be dry under a hedge, the hedge wants a lot of water in summer, but the roots will go down a long way. Put a soaker hose on it, but complain to the council to make sure they don't do it again. If it dies, get a solicitor to send a letter demanding the full cost of replacing with established hedge, not seedlings. You can buy large hedging by the metre from specialists who will install it for you.