Does this have to be on concrete? Can it just sit on the ground with no digging?

We recommend anchoring our products on either concrete footers or a concrete slab to make sure it can withstand the 100 mph wind speeds it was rated for, as it was only tested to withstand the winds by being anchored.

It can be rested on dirt/grass. The 100mph wind rating is only for when it is anchored down to concrete.