False. As far as we know, he farmed hemp for economical purposes.
Both George Washington and Thomas Jefferson grew hemp at their farms. In Virginia, hemp was promoted at the time as an alternative cash crop to tobacco, since it did not deplete the soil as much. Hemp was also useful for rope, paper, and clothing. Now, even though there was no social stigma attached to smoking pot at the time, there is no evidence to suggest Washington also smoked the plant. Having said that, Thomas Jefferson did at some point trade hemp seeds with another farmer in Missouri, which by many modern standards would qualify him as a dealer.