I do that with anything that goes directly in the ground here. We are super sandy. My Grandpa and Aunt always suggest adding peat, composted manure and soil from the garden center. I haven't added any peat because the ground already drains too well. I'm trying (3 years in) to get some rhubarb going in the ground. It's struggling. I think we are a bit too hot here but the fast draining soil doesn't seem to help. Part of my landscaping work the other day was digging around the plants and adding soil and manure.You could do what foxxycat does and dig a hole and replace the dig with the store bought soil.