Which Spirea did you get?
I have 'Goldmound' which recieves sunlight for only a few hours in the afternoon. The leaves stay bright yellow in spring then gradually turn rather green as the season goes on. I think it would have stayed bright yellow if grown in full sun.

I think spireas are very adaptable, although generally preferring a mostly sunny site. For example, I have a Spirea Japonica Shibori growing in a pot in full sun. It's predecessor lived in a pot in medium/full shade. The newbie is doing just as well as the old one [fantastic], but I have to be more careful to keep it watered.

Spiraeas (note spelling) are some of the most adaptable and hardy shrubs. They are not fussy about soil or light conditions although will not bloom very well in heavy shade and those offering colored foliage will not develop proper leaf color in much shade. Not especially drought tolerant, so offer summer irrigation; neither do they appreciate overly wet areas.

I planted several a few years ago. The one on the south side of the house is in full sun and it is huge and super looking. The three on the north side of the house are not as full and big. They only get about 3 to 4 hours of sun. They have actually stretched away from the house to get more light. They look okay but not as robust as the one in full sun. They were all planted at the same time and were close to the same size.

gardengal48 - the formal scientific (Latin) name uses the extra 'a' but common usage (and as far as I have seen, most nurseries) drop that 'a' -- in most of the dictionaries I checked, the spellings were noted as being alternatives. I also noted that the several horticultural guides I consulted *all* used spirea (not spiraea) when specifically referring the the japanese forms; using spiraea only when formally designating the latin name.

For the fun of it, look at link for Ohio U's spellings - all in one entry :) --- but I think we can be forgiven for not using the extra 'a'.

Here is a link that might be useful: OSU spirea facts