We have a large forsythia bush which is right at the front of a deep flower border, I dont fancy trying to dig it out as it is 8 feet tall and the same across. Do you think it will regrow if I coppice it back to 18 inches of main trunk? If I could keep it to about 3-4 feet after that then I woukd be happy as the birds seem to love it in the winter.
Forsythia is pruned after flowering and you can cut them back as hard as you choose without killing them. To be on the safe side, why not take a few cuttings?
To keep a normal one at that sort of height is going to take some fairly hefty pruning every year. There is a dwarf one called Maree D'Or which only grows to about a metre by a metre.