Answer: It is possible that a male pollinator would increase the berry production on your holly trees somewhat, although it is also possible that production will just naturally increase as the plants mature. (English hollies (Ilex aquifolium) as a group are slow to produce heavy crops.) It is also possible that there is already a suitable pollinator in the surrounding neighborhood. In any case, the nursery where you bought the three you have should be able to supply you with an appropriate pollinator.
The following companies sell a selection of hollies; ask their customer service department which holly would be the best choice, since the plants need to be compatible.
Carroll Gardens (Maryland) 800-638-6334
Greer Gardens (Oregon) 800-548-0111 or 541-686-8266.
Q&A Library Searching Tips