When planting apple trees, be sure to take in account their pollination requirements. This includes bloom time, tree configuration, their Ploidy and tree spacing. You will want to plant trees closer together that bloom at the same time and/or bloom times overlap. For example, if in a row, earliest bloom time at one end and finish the row with the latest bloom time. You will also want to watch tree spacing. Plant trees according to the rootstocks requirements.
A diploid apple has two sets of chromosomes with 17 chromosomes per set for a total of 34. Diploid apples require another diploid apple for good pollination. Make sure the apples that need to pollinate each other are in close proximity and their bloom times overlap. All diploids are decent pollinators for other diploids. However, if possible, avoid using the cultivars parent as a pollinator. The Winesap apple is a diploid but has defective pollen, treat it as a triploid.
A triploid apple has three sets of chromosomes with 17 chromosomes per set for a total of 51. Due to the odd number of chromosomes, cells won’t divide evenly. Triploid apples require two diploid apples for good pollination. When planting a triploid apple be sure to plant diploid apples near the triploid apple. Also make sure the diploid and triploid apples bloom at the same time or at least overlap to help ensure pollination.