The way I plant my garden the rows are spaced 3 feet apart and plants 1 foot apart in each row. I till the entire space as deep as I can which right now is about 1 foot or 30cm. I think initially I can do a coil on each of my two cherry trees as I don't mess with the ground around them. I have a bunch of copper wire, tubing, and even braided from shielded coax to work with.