What does the narrator dig up in a flower bed that causes his getting a spanking?

The narrator digs up a number of colored bottles, which serve to decorate the flower beds. He wants to see if they grow like the flowers.

I can see in this half vision a little house—I am quite sure it was not a large one—I can remember that flowers grew in the front yard, and that around each bed of flowers was a hedge of vari-colored glass bottles stuck in the ground neck down. I remember that once, while playing around in the sand, I became curious to know whether or not the bottles grew as the flowers did, and I proceeded to dig them up to find out; the investigation brought me a terrific spanking, which indelibly fixed the incident in my mind.