Update on my kohlrabi! He was incredibly slow growing. For the longest time, all he had was a few leaves poking out. Of course, I planted him with broccoli raab, which grow big strong stalks that were hogging the light. Finally, his leaves got bigger and he finally formed the characteristic kohlrabi "bulb."
The raab was beginning to bolt and my catnip was almost done as well, so I decided to clean out the garden yesterday. Here's the kohlrabi in the garden (partially blocked by that determined raab!). The bulb part of the plant kind of grew up in the air, with some of the leaves propping it up.

Here it is once out of the garden:


I haven't tasted it yet. I'm going to steam it with some broccoli for our side dish tonight for christmas dinner (we're making braised lank shanks).

So, my experiment shows that kohlrabi can be successful in the AG, but it is very slow going!