What do the pollination groups mean?
With the modern housing estates, the gardens are closer together and smaller. In which case it may be beneficial to have another tree planted in close proximity. If there are more older properties nearby, these tend to have larger gardens, and normally a fruit tree. In which case a pollinator is not required, providing there are enough bees about. The selected two varieties must be in the same pollination group or the adjoining group ie group 2 and 4 will pollinate group 3 as will any others in group 3. Some people use the A B C instead of 1 2 3. Some varieties are self-fertile.