Solo garlic is planted in the late spring/early summer and harvested late summer.

Regular garlic is planted in the fall and allowed to over-winter then harvested around mid-summer.

The clove forming process is triggered by reaching enough time at cool enough temperature. 50-60 days below 10C or 30-40days under 4C for most cultivars. There is some variation based upon genetics.

https://doi.org/10.1016/j.scienta.2015.07.018