Is they a stray male cat around? I find they spray the territory?

Try disinfectant - it's a 'cleaner' smell than cat wee. Diluted, it shouldn't harm your hedge.

What plant is your hedge?

One way of trying to prevent cats from spraying up your hedge is to put olbas oil onto tea bags around the base of the hedge, the appaently hate the smell, if that fails another mentod is to put household ammonia into small jars around the base of the hedge, again they dislike the smell.Hope these tips work.