Hello an.d welcome to GOY Noreen

Sorry dont know as I never prune mine.

But now buds are growing on rhodies for next years blooms.

You really need to select a variety that grows to the size you want. if you must prune I would do it immediately after flowering but you might lose next year's flowers.

Like Scotkat we never prune ours but as Stera. says immediately after blooming and you still risk losing the next year's flowers.

Thanks to everyone who offered advice about my rhody in a tub. I was worried that I`d lose next years flowers but the plant looks very leggy so out with my pruners, short time pain for long time gain.