(1) Here's what I found regarding blueberry pollination @: http://www.noursefarms.com/planting_gui ... guide.html
"It is best to plant at least 2 blueberry varieties for good cross-pollination. Cross pollination leads to bigger berries and more of them. Any combination of varieties will work
(2) Here's what I found for "Greengage" - I'm not sure if the "Early" is that significant? - @: http://www.keepers-nursery.co.uk/search ... ?id=EARGRE
"Early Greengage is self-sterile
and requires a pollinator to produce a crop."
(3) You said: "I imagine apple trees that are double grafted will pollinate each other."
I agree, and assume someone at least did that homework... Here's what I found on the Cox @ http://www.keepers-nursery.co.uk/search ... P&pageno=9
Cox's Orange Pippin is listed as: Self-sterile
. Golden Delicious is
a pollinator for Cox's Orange Pippin, Granny Smith is not.
Keep us posted