"So,what cha wearing under that dress?"
OK,maybe not.Remember it's a landscaping job.You're not hiring a rocket scientist.Just ask them what their experience is in regards to landscaping.Do they have any problems working outdoors,in all types of weather?
How long were they at their last job?Why did they quit or were they laid off of fired?
What part of landscaping do they enjoy the most?
I would have asked them to either fill out an application or turn in a resume first though.Then you can get some idea of their background.The interview would then be used to see what kind of person they are.
Go light on them,but not too lightly.He/she is probably going to be a little nervous,so break the ice with a joke or something.Smile and be pleasant to them.
My favorite interview question is "Would you rather be the best person on the worst team, or the worst person on the best team, and why?" To me there's not really a right or wrong answer, but you can learn a lot about the person by how they respond to the "why" portion of the question.