This is one way to make small tree circles. It is a nice way to clean up the base and protect a new tree.
Step 1: Level and Clean Around Base
I like to use a trimmer to clean up around the base a bit bigger than your circle will be.
Step 2: Lay Out Circle Template Around Base.
I used this pre - made rubber circle I got at Home Depot as my template. Garbage can lids or even hula hoops work well.
Step 3: Dig Around Template.
You can use an edger for this but for the smaller circles I like a hatchet just because it works good.