The info about earning acorns mentions acorns for landscape photos. I've posted photos to the plants database and received an acorn, but never when I posted landscape photos (even when I've tried tagging them, though the tags often move). Am I posting them wrong? (I'd love to win a raffle some day!) Thank you!

You do get one, just not a notification for it as you do with the adding to the database. Next time you add a landscape image, check your count before and after.