You can do them in the spring, but to be honest I have always done them in the Autumn, you can go hard on them and they respond very well, I always use shears to trim them to down, on long established spirea they tend to get very woody in the centre so every year or two I cut some of the older stems out.

Thanks Julien

Use to do ours after flowering with the Hedge trimmer, right down to the base otherwise we ended up with millions of seedlings all over the place.

Thanks Owd. Should I wait until after flowering next year.

I used to dead headas soon as they finished like OWD to stop self sown seedlings. then in spring pruned hard to knee height. they responded well to firm pruning as I needed to keep them short-ish.

Dawnsaunt.. If they are too big then prune them back now. They are very tough as Julien says.

I'm glad you asked this question Dawn. I was thinking of getting rid of mine (although they have now reverted to green) but will try pruning them, hard and see how they go :)

If they have reverted to green they may not come back other than green when hard pruned Hywel. but it is worth a go.

Thanks everyone, I will prune them hard this week.
Good luck with yours Hywel.

Thank you both. I realise they will stay green now but I like the flowers so I'll keep them.