I have a grand old forsythia in my front yard as part of a large shrub
garden. It's 25 years old, and is now about a 12 foot radius
hemisphere. The problem is, it's getting so overgrown and "worn out"
that there is little new growth or bloom on it. I did some small
pruning two years ago which helped a little, but I think it's time for
something more drastic. And since pruning time is coming up, I'm here
for advice.

I know forsythias can take a licking and keep on ticking, so I'm
wondering how far I can cut out old growth on this one. It is a very
healthy plant with a good solid root system. I "think" I saw a
gardening show once that said you can basically cut the whole thing
off at a couple of inches above ground and, if the roots are healthy,
it will completely regrow as all new vibrant growth. Has anyone ever
tried that?