Green’s Dictionary of Slang

(drugs) intoxicated by marijuana.

1960		E. De Roo Big Rumble 124: Some took drags on the weed and passed the sticks around. Twitch warned them about getting potted.
1968		‘Sl. of Watts’ in Current Sl. III:2 38: Potted, v. High on marijuana [...] I was potted out of my mind yesterday.
2014		in Guardian 21 Jan. 🌐 You. Your avatar is a cultural catastrophe. Stop boozing and get potted .