Yes it will hold as a cut for about 5 or so days, as long as you cut it in bud stage, showing colour, just prior to flowers fully opening. Cut open it will shatter. Sorry this response is a day late.
Cheers Kim
Billabong Fresh Flower Farm

Thanks Kim, I used a bit of spirea today in a few bouquets I sold at the market but the stems I used were fully open and did seem fragile. It also didn't work very well for the type of small arrangements I was making. It's natural form is a drooping arc which is out of scale for my tiny bouquets.