Why Some Trees Need a Partner at All
Self-fertile vs. self-sterile isn't about the flower's biology being broken — it's a mechanism many fruit trees evolved to force genetic diversity. Self-sterile varieties reject their own pollen at a genetic level, so no matter how many blossoms and bees you have, a single tree alone will flower beautifully and never set fruit.
Bloom timing matters more than variety name. Two varieties can be technically compatible but still fail to pollinate each other if their bloom windows don't overlap — one's already dropped its petals before the other opens. That's why the groupings above are based on bloom time, not just species.
Even self-fertile trees benefit from a partner. A self-fertile tree will set fruit alone, but most varieties still see better fruit set and larger harvests with a genuinely different variety blooming nearby, since cross-pollination is generally more efficient than a flower pollinating itself.
Distance matters. Pollinator trees generally need to be within about 50–100 feet of each other for the bees carrying pollen between them to be effective, closer in windy or low-bee-traffic locations.