Cannabis is known as a wind-pollinated plant.
With just a steady breeze, it may carry pollen up to a 30 mile radius, give or take… with a strong wind, the distance could be hundreds of miles.
If you are growing male plants to harvest their pollen, then they will need their own space to keep the pollen from escaping and getting to any unsuspecting female plants.
Keep in mind that male cannabis plants are safe until they reach maturity. Once mature, the pollen sacs start opening and releasing pollen… this is when males are a danger to your female plants… unless you want seeds.
When I collect pollen, I place the male in its own space, away from my females, and let the plant release as much pollen as it can. I put something under the plant to catch the released pollen, strain it to remove any impurities/pollen sacs, then place in an airtight container for later use.