That's why I use contractor bags. It creates a pot in the ground. Roots don't like heat and the pots will raise your soil temp in the summer if they are above ground. there are techniques for insolating you pots too if the ground is too hard -- but I won't go into that here. The hole keeps things cool, and the bags promote forcing as well as keep your environment clean and cool. Surrounding soil is not a great idea to use. For optimum performance, use mix and feed your plants from a clean slate.

peace. I cover all this in my video (had to get that in there).