Raised bed.
Recently read somewhere on internet, by some successful gardener person, that we should never plant in a dug hole. We should build raised beds or berms when we plant. So you could possibly dig a very wide, shallow hole, then add compost or organic matter to it (you can buy bagged compost or humus, don't buy garden soil or topsoil for this), Then add more to make a raised area and plant there. Mulch. Good luck.
Laurie