If you want to craft your own, you'll need a few things: silk flowers, wire cutters/pliers, heavy floral wire, thin floral wire to attach the flowers, and floral tape or ribbon.
The trick is to make the heavy floral wire crown part a little bigger than you think you need due to the ends of the flowers taking up space. Then it's a matter of attaching your chosen flowers to the base with the thin wire and smoothing all the edges with tape, if needed. Keep all those poke-y bits from digging into your head.
You can also use much smaller flowers if you're looking for something more subtle. But in this case, my motto is "more is more, bitches." Speaking of more, here are more detailed steps:
Head over to Kelly Murray's blog for more detailed instructions and photos to help you along.
BONUS FALL HAIR CROWN:
This was a flower crown I made for Halloween with a really similar process (plus a bunch of other floral doo-dads). This is more autumn-like or maybe even summer, if you're going for that. And don't think I wouldn't wear those point-y ears and crazy eyelahes to my wedding, too. I'm ALL IN.