They're a bit 'in the distance' to tell, Isolde. Could you please take close-up photos of the leaves and post your question again?

When I used to garden for my sister in law, she had a spirea similar to your picture. Your shrub could be Arguta (Perfect Plants) I used to prune it well back every year to about 6-9 inches. It seemed very vigorous and not to mind the pruning. I have the yellow leaved spirea with pinkish flowers. Each year they are either trimmed or pruned well back, according to how intrusive to other plants near to them. I left the ones in the front garden much longer stemmed this year to enjoy the bright colour of the new leaves early on after the long winter. In other words, leave them trim them or prune them, and feed them.

Thanks for the input Dorjac! I read in my book that depending on the type (sort?) of spirea you cut back completely or only the old branches. Knowing that I want it to grow as quick as possible, I am hesitating cutting it back completely...
Unfortunately I don't have a closer picture Spritzhenry... :-(

It's too late to do it this year, now. You'll lose the flowers. I cut my Spiraea japonica quite hard back several weeks ago.

S. arguta is about to flower - so it's the wrong time to prune that as well! I think that that one gets trimmed after it's flowered.

Hey again :-) You're so quick in answering, just great!
I don't think it is Arguta when I look at pictures on the net. But hey, as mentioned, the picture is quite unclear :-(
Let's wait till it flowers, and I'll try again with a better picture.
Thanks again!

OK. I'll watch out for it. :-)