Gary Wayne Bullington, 56, pleaded guilty to cultivating 6,289 marijuana plants worth $3,327,000.
Fifty-nine-year-old Trudy Elliott Jackson pleaded guilty to manicuring 1,574 marijuana plants worth $555,200.
The sophisticated underground growing operation was discovered under a barn on Kraft Road in Franklin, Ky.
Jackson and Bullington will be sentenced Dec. 14, 2006.
A third defendant, Ale Snoddy, also known as Charles Lawrence, pleaded guilty earlier. His sentencing is set for Nov. 21, 2006.