Historically, pollination has been overlooked when planting pecan orchards. The increased production you see from having the right pollinators in the right place is not always something you notice unless you have something to compare it to. The effects of poor pollination will also be more obvious in some years than others when spring weather conditions disrupt pollination.
I often hear someone say “There are plenty of seedlings scattered around near my orchard to pollinate my trees”. Just because there are other pecan trees around does not mean they are pollinating the trees in a particular orchard. In order to get effective pollination, the female flowers in your orchard have to be receptive to pollen from another tree at the time other trees are releasing pollen. Pecan trees will self pollinate but a large percentage of these nuts fail to develop, abort and drop off, or fill poorly.
Pollinators also have to be in the right place. Research has shown that pecan trees need a pollinator within 150 feet. This is why we often recommend placing a pollinator at every 5th tree on every 5th row if you prefer planting a solid block of one cultivar. On the other hand, if you block multiple cultivars in an orchard, change cultivars about every 4 rows. Pecan trees usually only release pollen for 5-6 days and female flowers may only be receptive for as little as 4 days so just a few days of the wrong weather conditions can wreak havoc if you only have a couple of cultivars in the orchard. This is why we recommend planting at least 3 cultivars in an orchard when possible. The greater the diversity of cultivars, the more you spread your risk.
Click on the pollination chart here to see which cultivars serve as pollinators for each other.