I found this tool in a hardware store, picked it up, used it, and I liked it. It does the job of making a hole large enough for my little trees to fit in perfectly. You can even drill deeper so you can improve the soil beneath. This auger is 24" long and almost 3" in diameter.
Just perfect to drill holes for the trees in bags.
You need to have a portable drill, with a 3/8" chuck or larger. If there are large rocks in the soil, this tool will not help you at all, I have drilled holes where there were rocks of up to 2 inches in diameter and it worked with a little coaxing. You can drill holes up to 20" deep if you want to go that deep, but for my trees, all you need to go is 7" deep. When there are no rocks, you can drill a hole in about 2 to 3 seconds with no effort at all.
The tool is guaranteed for life, so, if you break it, I will send you another one, all you pay is the postage. If you have a lot of holes to dig, I hope you have a heavy duty drill because a small one would run out of battery in a short time.
Unrelated uses - I wanted my wife to plant some echinacea I had in the greenhouse. Instead of the little shovel and other tools we used in the past, I attached the auger to my portable drill and gave to her to hold. Once she figured out how to use it, she went on her way drilling holes...at the end, we planted 60 echinacea plants in about 10 minutes. She then found some picky weeds, touched one of them them with a quick twist of the auger, and Viola! the weed was out. She spent the following 10 minutes weeding the rest of the garden with this newly found toy. She must have liked it!
I just know she will never use the weed puller again.