A full day's labor for a 16 year old or ANY employee is at least worth minimum wage. Meals are a nice fringe benefit, and I believe you would be required to provide drinks also, but you should pay him at least minimum wage. Landscaping is hard work.
SO!? "He doesn't have to pay for any of his meals." HE"s still doing the work isn't he? Not fair to rip him off just because he's a teen! Shame on you. You want to take advantage of him. He deserves the same pay as anybody else. Try $10./hr and do the work yourself next time!