The forsythia is vigorous and resilient. It can take a hard pruning. Depending on when you scale this large shrub back, you may forfeit blooms. No big deal if you’re looking to reduce its size. I had the same thing, a very mature one on a property I purchased. It was about 15’ wide by 12-15’ tall. I cut it almost in half. I pruned it to maintain its natural state and after two seasons, it was just beautiful. It’s easier to maintain rather than trying to force it into a hedge shape and it will look more appealing.
The forsythia is vigorous and resilient. It can take a hard pruning. Depending on when you scale this large shrub back, you may forfeit blooms. No big deal if you’re looking to reduce its size. I had the same thing, a very mature one on a property I purchased. It was about 15’ wide by 12-15’ tall. I cut it almost in half. I pruned it to maintain its natural state and after two seasons, it was just beautiful. It’s easier to maintain rather than trying to force it into a hedge shape and it will look more appealing.