The “origin” of pollen, is simply in the flowering plants, (perennial or annual), shrubs and trees (“wild” trees, “fruit” trees etc.).
Where exactly is pollen produced in these flowers?
In the anthers (male sexual organs) of flowers.
The foraging bees gather pollen from the anthers and transport it back to the hive for various uses.
For apitherapy, the most important types of pollen are bee pollen (collected by beekeepers with special pollen traps) 
It is also very important to know the exact origin of pollen used in apitherapy. So, we need to know:
- the geographical origin (country, area, place); mountain pollen is different in effects from plain or desert pollen;
- if the area is polluted or not?
- the plant (tree) sources for our pollen?
Knowing the plant (tree) sources of a pollen is extremely important because you can then better understand its pharmacological effects.
For example, linden pollen is similar in effect to the linden flowers used to make medicinal tea.