Looking at your situation and variables, I think you should research your soil a little. Find out what the ph is. I'm not sure what else you have that is in there, but they might thrive in a medium that is too acidic or something. As long as the ph is within range, say 6.5, you should be in perfect shape.

How about insects and such? Do you employ them or fight them?

Garden sounds fantastic to me, can you post any pics?