To send these to your lucky friends, look for the icon above on the left-hand side of the screen, click it and pop-up window with a friend selector will appear. Pick whom you want to send this gift to -- and voila!
If you receive a 'Fertilize All' gift, accept it and then look for it in your gifts box. Click 'use' and all of your crops will be fertilized, which means extra XP and bonuses when you harvest.
Send 'em now -- there's no telling how long these will stick around.