Apple trees are generally not self fertile and even those advertised as such will often be more productive if there is a second variety nearby(1). That doesn’t mean a second tree of the same variety. That means a second variety of apple: GoldRush, Arkansas Black, Dabinett, Yarlington Mill, and such. However, other factors also impact the ability of these varieties to cross-pollinate including bloom times. One interesting aspect involved in the pollination process is the ploidy of the variety. Ploidy is simply the number of chromosomes sets in a cell. Apple trees that are diploid have two sets and those that are triploid have three sets.
For reference, humans are diploid. We receive one set of chromosomes from each parent. Many apple trees are also diploid but not all. Unlike mammals, plants can more easily become polyploid, having multiple sets. You might think this would make them super pollinators because they have more chromosomes. However, it actually makes them sterile. They are unable to provide pollination. If you planted two tree that have overlapping bloom times and one was a diploid and the other a triploid, don’t expect the diploid variety to bear fruit. It will pollinate the triploid variety but the triploid won’t be capable of pollinating the diploid in return. You would need a third diploid variety to ensure good cross-pollination.
Most tree and orchard sites will provide pollination information but here is a nice list from Albemarle Ciderworks of known triploids(2). Note that many of these are worth the effort of having extra varieties for pollination if you are interested in making hard cider. Also, consider crabapples, which are usually excellent pollinators and great for cider.
- Arkansas Black
- Ashmead’s Kernel
- Baldwin
- Belle de Boskoop
- Blenheim Orange
- Bramley’s Seedling
- Crispin/Mutsu
- Fallawater
- Gravenstein
- Holstein
- Jonagold
- Karmijan de Sonnaville
- King David
- Newtown/Albemarle Pippin
- Rhode Island Greening
- Roxbury Russet
- Stayman
- Summer Rambo
- Tompkins County King
- Winesap
- Zabergau Reinette
So, when you are deciding on what apple trees to plant, remember to consider the pollination requirements along with disease resistance, climate hardiness, bloom times, chill hours, and how you want to use your apples.
(1) https://www.orangepippintrees.com/articles
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