I planted a teeny forsythia bush last spring - barely more than a few twigs, and it didn't even flower. This year it flowered but the few branches that it had have grown really long and straggly and are bending over. It obviously needs pruning to thicken it up for next year , but when and by how much? TIA x
The relevant RHS page here
http://www.rhs.org.uk/plants/details?plantid=802
places Forsythia into 'Pruning Group 2', which takes you here
http://www.rhs.org.uk/advice/profile?PID=197
which tells you to prune immediately after flowering (which, in your case, will probably have to be read as 'a.s.a.p.', since it's already flowered), with these instructions:
"Cut back flowered growth to strong young shoots lower down. Each year cut out up to 20 percent of ageing stems to near the base".
The two key things to remember with Forsythia is to prune soon after it has flowered.
And secondly, remove no more than one third of the older branches.
You should find, it will grow much more vigorously as it becomes established.