I have an irrigation system that was designed to water only the lawn (which does not need much water IMO) and a lot of garden that needs watering. How much work is it to add a drip zone to an existing irrigation system? I have a control box with extra zones.

My Control box is in my garage which is detached from my house, but close to the front of my house. Under my porch in the back of my house, I have a bunch of valve-like things that are part of my irrigation system. There are 5 or 6 of them, although I have 13 zones. They have pipes going out from them.

Would I need to put a new wire from the garage to the valve-like things? Or would I just need to add piping and emitters from the valve-like things? Since the exiting wire/s from the garage is buried, and the garage is far from where the valve-like things are, a wire would be a LOT of work.