Yes, corn grows to 6 to 8 feet high.
Marijuana grows to 10 to 12 feet high. Think you could spot that from your front door?
ROFLMBO! I've been shaking my head at these city folk too. They obviously don't know how small 320 acres is and think marijuana grows no bigger than a joint which can easily be hidden behind rows of canned corn. This guy's land is in the TX panhandle next to the NM border where there's nothing, and I do mean n-o-t-h-i-n-g, blocking his view. We have a bit over 400 acres of pasture (a huge difference from cultivated land) with hills and still can see most of it out the window. There is no farmer who doesn't know each and every blade of grass (legal or illegal) growing on his land. If there's anything growing that isn't supposed to be there, it is taking away from the income. That guy's farm is a "working farm" that feeds his kids and pays the bills, not a nice vacation place outside the city to commune with nature.
Oh, and it probably is true the old man was the only one in the county who didn't know what was growing out there. Check out the terraserver link for Farwell, TX.
http://terraserver-usa.com/image.aspx?S=14&T=1&lat=34.3833&lon=-103.0375