Hi, i have a 25m long by 8ft hight hawthorn hedge which looks very old, my problem is that parts are very bare and from the ground to about 600mm high there is not much hedge at all just trunks. Also im next to a road and you can see right through the hedge most of the year, my question is what can i do to fix this, i dont want to take it down so is there some sort of evergreeen hedge i could plant in between? Any suggestions would be helpfull.

thanks mark