When you plant blueberries, it's important that plant a mix of varieties for cross-pollination.
But getting the best results from cross-pollination involves more than just selecting the right blueberry varieties.
Because it’s also important that the cross-pollinating plants be close enough to each other, and that there aren't too many of one variety and too few of another.
For blueberry pollination, the spacing isn’t really super-critical for cross-pollination purposes. You have some flexibility.But you do want to have the cross-pollinating varieties reasonably close together.
For example, if you have a variety on one side of the yard, and a pollinating variety over on the other side of the yard, the blueberry pollination results may not be the best.
If the plants are widely separated, then bees will be less likely to visit both varieties in one foraging trip. And that means poor cross-pollination.
Quite often, one particular variety of blueberry is planted as the most desired variety. Other varieties are grown mainly to provide pollination for the favored variety.
When this is the case, there’s likely to be considerably more of the ‘star’ variety than the ‘supporting cast’ varieties. That’s OK as long as things don’t to get too out of balance.
I don’t know of any university recommendations for cross-pollinator ratios. So I’ll just tell you that based upon my own experience, I’d prefer not to exceed a ratio of around 3 to 1.
So for every 3 plants of the ‘star’ variety, I’d plant at least one of the pollinating varieties.