I am doing some cupcakes for a wedding next week. They are all going to be a little different--with all sorts of flowers/leaves on the tops. When I did a test run, I found that the flowers went soft after sitting on the buttercream for a while. I'm wondering if there is a way to avoid this as the bride would like to pick up the cupcakes a whole day in advance. Does anyone have any tricks??

Don't store the cupcakes in an airtight container. An airtight environment will cause more problems for your gumpaste than the icing.

Refrigeration is also the enemy. If the cupcakes have to be refrigerated, then your bride may have to recruit someone to place the flowers on the cupcakes when they're set out for display.

totally dry royal icing shouldn't do that, but gumpaste always does for me. And if you dry out the cupcakes, that's an even bigger bummer.

Agree with Diane, air-tight containers are a gumpaste flower killer. I only have that problem with cupcakes in air-tight containers. Most flowers can take refrigeration if the air can circulate around them. If your cupcakes can take room temperature then I'd leave them out.

I've never had a problem with gum paste going soft on buttercream in the fridge. Most of the decor I use for stand-up or hardier pieces I use gum paste and they are always refrigerated and hold up not only well...but stay hard. I did a bunch of cupcakes with a purple violet on them and had them in the fridge overnight and for several hours before delivery. They held up very well.
I use Wilton's pre-made gum paste and it seems like once it's dry...it's DRY. I've also stored extra flowers and other small decor in an airtight plastic container. In fact I'm going to use some small yellow butterflies I made a couple of months ago on a cake I've got due tomorrow. Our humidity has been horrible lately and the buttercream on my cake keeps getting soft quickly even when I've had in the fridge for hours...but the gum paste items are just as dry as can be. Check into the Wilton's stuff. There's not much of Wilton's I like, but this stuff works great for me.

Thanks for the replies everyone. I just worry that if I leave the cupcakes out at room temperature that they will dry out as the icing never goes right to the edge of the cupcake. Maybe I'll do a trial run..

You are right, you will have a problem of dry cupcakes.
I know there are tons of beautiful cupcakes with fondant decorations on them. But you have to figure out which one you want, a dry cupcake or a fondant decoration. Bear in mind picking them up a day in advance means they will be dryer than normal anyway, assuming that you are baking them the night before. The only way to help this is an air tight container. The bride or one of her helpers may have to decorate the cupcakes the day of the reception themselves in order to prevent this. Once they are out on display it will be okay. But if you are not delivering and setting up, then it will be up to them to take care of that part.

I have not used a gumpaste decoration myself, but it might be worth trying if it worked for the PP.

Royal icing will also melt, but in my experience it takes longer than fondant.