[Casey76]

I have a forsythia which is running amok after i forgot to prune it back last year.  It has just finished flowering.

Can I trim it back now, or do I have to wait until later in the year?

[mumofstig]

Now is the right time to prune 

The rule of thumb for pruning flowering shrubs..is to prune just after flowering, so you timed it just right

[DavidT]

I totally agree with Lesley. Now`s the time, and you can give it a bit more than a trim.

[Casey76]

Lol David.  At the moment there are branches (can you call them that?) which are about 12-15 feet long... soon to be reduced to a more sensible 3 feet!