If you grab a bud and roll it in your palms, hemp will just fall off but smoking marijuana will be sticky … if the smoking marijuana is being actively cultivated, then the plant will have been “topped” creating an more bushy plant with many many flowers … just growing wild either plant will grow tall and straight with just one or two flowers at the top …
Using ditch-weed to camouflage a grow operation would be a bad idea … you’d lose your genetics in one season due to cross-pollination … unless you male for miles around, but that would be far too much work … plus you won’t find large fields of ditch-weed where something else can be grown, like corn or soy beans … you find it in roadside ditches and fence-rows … I’m not saying no one in history ever tried this, but it wouldn’t be effective over the long haul … better to move to California and grow there …