Caleb grows his in the back half of the greenhouse behind Miss deCarte's. Alphie keeps an eye on the general goings-on when Caleb is preoccupied with school, in return for which he gets free drugs and occasional heavy lifting. It's a good deal for all involved, which is one of the things Caleb enjoys about Meminisse, how the barter system is alive and well.
He lets whether or not his sense of humor is a rollicking good time pass without comment other than a curly-grinned 'thanks,' then: "Is that what you're going for? Are you projecting not-nice on purpose, is what I'm kicking at. You can feel free to tell me where to get off, it won't be any skin off my--whatever."
The gesture that accompanies this is loose, not incisive as one might expect with a relatively penetrating question, but--as he says, she is free to tell him to mind his own apian byproduct.