For those who've been asking the obvious question about mailing...
As with most embellishments, this one is fragile and may not hold up well through the mail. I shopped three stores and one USPS looking for those corrugated heavy-duty CD mailers (that I used to see EVERYWHERE) with no luck. This seemed to me a good choice for keeping my leaf from being crushed in transit. As I didn't have one on hand and could not find one anywhere, I improvised and mailed this card in a SU! spot box. It was snug, but it fit and did the trick.
I later found/ordered THESE
via Amazon to keep on hand for mailing future cards with super fragile embellishments. An A2 card (5 1/2 x 4 1/4) inside of an invitation-sized envie (4 3/8 x 5 3/4) just fits lengthwise, so be careful with your measurements if you decide to go this route for mailing!
The final cost of these mailers with s/h and tax comes out to about $1.20 each. An insane amount of money for mailing a card, but if I've gone to all the trouble of crafting something like this, I want it to arrive unscathed. Not sure yet what the cost of postage will be. Whoever started the silly rumor that making greeting cards is cheaper than buying them was clearly delusional!
Hope this helps. If y'all have any better/more economical ideas, feel free to share 'em.
PS Shop around. Some places that sell these online are MUCH more expensive than others.