What I would say would depend on how well I knew the couple. If naming their kid “Garden” seems to fit them and their lifestyle, I would probably keep my mouth shut. If I know them well and can think of a hundred reasons why “Garden” is a lousy name for their unborn son, I would probably say something along the lines of “that could be a really interesting name for a kid, but I am not sure how it would work for an adult” or “Garden Alexander Smith, hmmm, you could have a challenge with his initials if he ever wants a monogram on something.”