That's all well and good geo but it doesn't really work as a defence , the onus is on you to prevent illegal use of your property and that includes regular inspections , if you are found to be guilty of allowing the property to be used for illegal purposes then the property can be siezed.
Often in a court the choice to "remain silent" can prove to be disastrous as many see it as a sign of guilt.
If ganja was found on your property then you can almost guarantee that the police will seek a warrant before coming knocking on your door.

Never allow anyone to grow on your property except yourself, never grow on another mans land , then if the shit hits the fan it's only you taking the flak.

I cannot accept involving innocents in any crime I may choose to commit and I cannot advocate anyone elses doing it.