My first guess was vanilla, but since that one is already covered, here are some other ideas:
Illegal plants (like marijuana)
I'm sure that when you think about illegal activities you'd think that robots are your best friends, but there are a couple of reasons why it might not be true:
- Robots will want power, and you will already be draining more than your fair share from the network. The more power you use, the more you stand out, so someone may come by and start asking questions. It already happens: http://www.postandcourier.com/article/20120129/PC1602/301299979 and the more robots you have, the bigger the risk
You have to get them somewhere. You also need someone to maintain them in good condition. It would be probably be easy for government goons to follow all transactions involving new robots, and most transactions involving second-hand robots. Buying several such robots without having anything bigger than a garden (officially, of course) will once again draw attention to yourself.
NSA spying. How hard would it be for spy agencies to secretly install some tracking device in every robot ever produced? Probably easy, assuming they don't do that already. Your new friend will lead the police right to your doorstep.
Records. Everything the robot will do, probably is going to be recorded (openly or secretly). In both cases you probably won't be able to ensure, that the machine won't be a walking pile of evidence against you.
Robots don't have feelings. The can't be bought, bullied, reasoned or negotiated with. They just want to do what they programming tells them to do. You can make a human shut up one way or the other (dead men tell no tales), but with a robot you can never be sure.
Yes, it's hard to find humans who can be trusted, but with robots it's outright impossible.
I think this is obvious - everything the Amish eat, will be produced by humans.
Also we can add to this category all the people, who believe, that nothing tastes like a fruit from a tree watered with your own blood, sweat and tears, from your own garden.
Many plants have dual purpose - they both produce food and look pretty. Cherry tree is a good example. They will need a lot of human attention during their entire lifetime.
For the first couple of years they will be grown on a farm. Surely, some automation will help, but unless there will be a human to oversee whether they look pretty, it will be hard to sell them.
Once they are sold and planted in someone's garden, there will probably be little to no automation - robots are expensive and without economics of scale there will be no reason to buy them. Especially, that you need a meatbag anyway to make sure, that it still looks pretty.
And yes, it counts as food - as stated above, some people just prefer things they grew themselves.