They grew hemp, which this quote erroneously identifies as "marijuana". The two are both Cannabis sativa sativa, like Dachshunds and Greyhounds are both Canis lupus familiaris. But (again like the dogs) the plants are bred in vastly different ways, to create strikingly different physical configurations, and for completely different purposes.

Hemp is the best natural fiber known, and a number of the Founding Fathers grew it for that reason. But there is no point smoking it unless one wants the granddaddy of all headaches and no buzz.

Modern smokeable "hemp" is actually cannabis grown as "marijuana" (shorter plants with abundant smokeable flowers) but with a higher than usual CBDa content and very low THCa content of under 0.3%.

There's no reliable evidence that the Founders sexed the plants (to increase cannabinoid-containing resin, discarding males prevents pollination and causes females to overproduce resin), grew them for anything other than fiber, or smoked them.