I haven't a clue as to what caused it to get so big but definitely use it for planting in the fall. My experience with naturalized garlic is the complete opposite, the plants grow in clumps and the bulb size diminishes to almost nothing.

Rodney

Hope that I uploaded correctly. The bulb on the left is my typical "largest" blub that I will harvest. The one on the right is my, well....my Frankengarlic

I doubt that it is regular garlic but perhaps ELEPHANT GARLIC, which technically, is more like leeks and onions in flavor.

PS
how come it does not have roots ??!!

I am sure that it is my garlic. I've been using the same batch for at least 15 years. I hardly ever buy garlic and never Elephant "Garlic". Oh, the no roots? I ran out of my stuff and at first I was going to cook with this baby, just to taste it. After cutting off the roots, I changed my mind and decided to see what happens next year, after planting it this October.