Once flowers open in the spring, we’re hoping for warmer weather so the bees will transfer pollen and for rapid pollen tube growth.
As we all know, apples require cross pollination, so for example Golden Delicious pollen will not fertilize Golden Delicious flowers. We rely on bees and other insects to transfer pollen from one apple variety to another. Most apples will successfully pollinate most other varieties, with the exception of triploid varieties such as Jonagold and Winesap. Once the pollen is transferred to the stigmatic surface of a flower, the pollen needs to be recognized and then grow down the style to fertilize the ovule resulting in a seed and fruit set. Generally, without seeds, apple fruits will not develop adequately. The problem here is that the ovule is only receptive for a few days so rapid pollen tube growth down the style is necessary. And this all depends on the temperature. When it’s 50-60 F, pollen tube growth is slow, and pollen tubes hardly grow at all when it’s cooler than 50F. Above 60 F and pollen tube growth is much quicker and fruit set is much more likely. So when we have open flowers, we’re hoping for days above 60, and preferably in the 70s. Cooler weather in the forecast for next week is not favorable for good pollination. Let’s hope it turns out to be warmer than the forecast is predicting.