Without some gouges in the sides the tree or plant will quickly become root bound like some of your houseplant purchases of yesteryear. Root bound roots begin to lose their effectiveness as they compete for the limited space in this bowl they are in. As they get bigger they begin to crush one another, thus stopping all above ground growth. The gouges will trap them and force them to continue outward in the the soil.
Remember, everything is only as good as its foundation. I know chipping through the clay is a tough job; but it’s best to not have planted at all, than to have started only to say “this is good enough” and ending up with a shallow grave for your purchase.
If you have any questions feel free to e-mail me at NiemeyerLandscaping@Gmail.com or post a comment on this Blog. And like us on Facebook at Niemeyer LandscapingFor more Landscape and garden info check us out at www.NiemeyerLandscaping.com