grow some indica dominant plants and let them go really late, so when ya think thewy are done , leave them another 2, 3 weeks, should do the trick. the most sleepy weed ive ever seen was some cherry pie left on the plant outdoors till first week in november(cali od lowers), the herb turned almost black , the herb changed to serious knocvkout sleepy herb, not much high but the shit made me sleep so good .it showed me how ya can make same plant give ya different herb by harvesting at different times. lol last harvest i had mostly clear trichs and my edibles made me trip pretty good , hearing shit while i was laying in bed ha ha good luck bro , i use beer to sleep btw it works, makes ya fat and expensive
Disobedience is the true foundation of liberty. The obedient must be slaves.
Henry David Thoreau