I have just bought a few fruit trees and need to know if I need other types
or more than 1 of each for them to fruit.
The ones I have are Nectarines, and Valencia Orange.
I also have a single apple tree with both Golden Delicous and Granny Smith
grafted on. Will this single tree polinate 2 Sundowners and 2 Galas situated
around it? The Sundowner tag says it it semi self fertile. Does that mean it
will fruit by itself but not to it's full potential?

Thanks
Andrew