Posted: 30/04/2017 at 19:54
My personal inclination would be to hack it and then dig it up but then I don't like them.
However, assuming they want flowers next year they should cut about 1/3 of all the stems back to the main stem now. They can then shorten the remaining stems to a size and shape that suits them. If they repeat this every spring after any flowering finishes they will have renovated their shrub over 3 years - as long as they don't cut out the newest shoots next year and the year after.
Thereafter, they just need to cut back all the flowered stems as soon as flowering finishes. Forsythias flower on wood produced the previous year but an older one that's been neglected might go onto shock if you take out all the stems in one go. A spring feed wouldn't hurt.
Last edited: 30 April 2017 19:56:06