Leaf polish is a standard product used in almost every flower shop. It is sprayed on greens (and fresh plants) to lock in moisture and seal the leaf, giving it a longer life.
Flower shops use large cans, but I have smaller cans (4.2 ounce) available for DIY brides that is usually plenty for one wedding.
Fresh greens sometimes have a dull or splotchy look when misted with water, due to the mineral deposits left after the water has evaporated. Leafshine prevents this, giving a nice clean look to the greenery.
Spray this product on greens only. Fresh flowers have a different kind of sealant that slows petal transparency. (I use Finishing Touch).