Male to female distance - proximity for effective pollination?

What is the maximum distance male and female plants can be apart for effective cross pollination?

 

It depends on how they are pollinated, if by flying insects, I would say up to a half mile. By crawling insects just a few yards. But by wind pollination it could be miles.

 

Also a lot of plants are self pollinating (self fertile) they possess both male and female organs (stigma & anthers) the stigma is a little slower growing within the flower and has to push its way through the anthers(pollen carriers) picking up the pollen often the flower is fertilized before it actally opens.

quite right David some grass pollens more than 20kilometers,some pine pollens thousands of kilometers,some rust spores have travelled continents and they say g m crops are safe.