The Cortland apple is a popular variety known for its crisp texture and slow-browning white flesh, making it a favorite for fresh eating and salads. Cortland apples are not truly self-pollinating and rely on a compatible partner tree to achieve a substantial harvest. While some fruit may set without a partner, the yields will be significantly improved through cross-pollination. This requirement for external pollen is shared by the majority of apple cultivars grown today.
Understanding Apple Pollination Categories
Apple tree varieties fall into three general categories based on their pollination needs, determined by the genetic makeup of their flowers. The first group is “self-fertile” or “self-pollinating,” meaning the tree can produce fruit using its own pollen without needing a different variety nearby. Even these varieties often produce a heavier crop if cross-pollinated with a partner.
The second category is “partially self-fertile,” describing trees that can set some fruit with their own pollen, but the resulting yield is small and inconsistent. The final and most common category is “self-sterile” or “self-incompatible.” These trees cannot produce viable seeds or fruit without pollen from a genetically distinct apple variety. This incompatibility involves a genetic barrier that prevents the tree from fertilizing itself. A lack of successful cross-pollination results in “June drop,” where the tree sheds small, unfertilized fruitlets prematurely.
Cortland’s Specific Pollination Requirements
The Cortland apple cultivar is classified as partially self-fertile, but it functions best when treated as a self-sterile variety. Relying solely on its own pollen results in a minimal harvest, making a partner tree a necessity for fruit production. This requirement stems from the need for a different genetic source to ensure successful fertilization of the ovules within the flower.
Cortland has a mid-season bloom time, meaning its flowers open after the earliest varieties but before the latest ones. For effective cross-pollination, the partner tree must have a significant overlap in its blooming period with the Cortland tree. The transfer of pollen between these two different varieties is primarily achieved by insects, such as honeybees and native bees.
The proximity of the pollinating partner is a physical consideration for the transfer of pollen. While bees can travel distances, the highest rate of successful pollination occurs when compatible trees are planted within a range of approximately 50 to 100 feet of each other. Planting trees closer together maximizes the chances of a pollinator carrying the foreign pollen directly to the Cortland blossoms.
Selecting Effective Pollinizer Varieties
To ensure a robust crop, the chosen pollinizer must meet two specific biological conditions: bloom time overlap and genetic compatibility. Cortland is a diploid variety, meaning it has two sets of chromosomes, and it requires another diploid variety as a partner. Triploid varieties, which have three sets of chromosomes, produce sterile pollen and cannot be used as effective cross-pollinators for Cortland or any other apple.
Several popular diploid apple varieties are excellent partners for Cortland because their mid-season bloom times align reliably. Varieties such as Gala, Fuji, Honeycrisp, and McIntosh are widely recommended as effective pollinizers. These partners provide the necessary viable pollen and offer the grower a second type of apple to harvest.
Crabapple trees are also highly effective general pollinizers and can be a space-saving solution in smaller gardens. Many crabapple cultivars are diploid and produce abundant flowers with a long-lasting bloom period that easily overlaps with Cortland’s flowering time. Choosing a crabapple or a second fruiting variety that shares a similar bloom window ensures the Cortland tree receives the foreign pollen it needs to yield a full and healthy harvest.