forsythia needs reducing in size before extension, when to prune?

[sacbina]

Probably needs reducing by a third. It's a healthy, bushy specimen so don't want to lose it. Building work due to start 1 September.

There's also a red robin which could do with a bit of a prune.

Any advise?

Prune forsythia now straight after flowering. It's very hardy as long as its in a sunny spot it'll be fine. Sorry I don't know what a red robin is

Thanks for replying. The forsythia is well past flowering, but I presume then that I should do it sooner than later.

The other is a photinia red robin

The photinia is ok i think my book says it needs trimming regularly to keep the 'red' leaves .

It can be pruned now - TBH it's impossible to damage Forsythia, you could cut it down to the ground and it would be a healthy looking shrub by next spring but TBH, if it's that big and that close to new brickwork, I think your builder should be recommending it goes altogether.

Thank you
Busy weekend ahead....