He thought of ScrOG in jail
On October 26, 1989, the DEA in conjunction with dozens of other law enforcement agencies raided hydroponics stores in 46 states, arresting 119 people, seizing several indoor gardening shops and thousands of cannabis plants. The largest single seizure belonged to Wolf Segal (Farmer in the Sky), 12,000 + plants growing as "Sea of Green" (SOG). Operation Green Merchant became known by the early cannabis pioneers as "Black Thursday" as many people swept up were hauled off to serve time in jail.
The Sea of Green method and cloning cannabis plants were techniques learned and brought to the US from Holland in the 80s. SOG is used to create "perpetual harvests". The method involves high plant counts per cu ft/m and short grow cycles. Clones are introduced to 12/12 flowering with little to no veg cycle. Many growers cannot use SOG due to local plant count limitations.
It was the high plant count associated with SOG that got Wolf "top grow bust" recognition. And while serving time in jail, he came up with the concept of Screen of Green (ScrOG). The concept was to grow short bushy plants with longer veg cycles that were 2x3 times more productive than traditional growing methods. This method would allow Segal to have big yields with lower plant counts.
Wolf explains the concept in this video shot at IndoExpo, Denver 2017.