All About Hazelnut Pollination
Introduction
Hazelnuts are unique nuts that have a fascinating pollination process. Unlike most plants that fertilize a few days after pollination, hazelnuts take four to five months! This unusual process and the need for cross-pollination make growing hazelnuts a bit more challenging but also very interesting.
The Long Journey of Hazelnut Pollination
The journey of hazelnut pollination begins over a year before the nut is ready to be harvested. Here’s a detailed breakdown of the process:
Male and Female Flowers
Hazelnut trees are monoecious, meaning they have both male and female flowers on the same tree. However, they are self-incompatible, so they can’t fertilize themselves.
Male Catkins
In mid-May, male catkins start to form. These catkins are clusters of male flowers that produce pollen. They reach maturity in December or January.
Female Flowers
Female flowers start to form in late June and become visible in late November to early December. They are bright red feathery tufts with long styles that are receptive to pollen.
Pollination
Peak hazelnut tree pollination occurs from January through February, depending on the weather. During pollination, pollen from the male catkins is carried by the wind to the female flowers. Once the pollen reaches the stigma of the female flower, it germinates and grows a pollen tube down the style.
Fertilization
Four to seven days after pollination, the pollen tube reaches the base of the style and its tip becomes blocked off. The entire organ then takes a break.
Ovarian Development
Pollination jumpstarts development in the ovary, which is the part of the flower that contains the ovules. The ovary slowly grows over four months, and then speeds up. Most of the growth occurs in the next five to six weeks.
Fertilization
Finally, four to five months after pollination, fertilization occurs! The pollen tube delivers sperm cells to the ovules, resulting in fertilization.
Nut Development
Nuts reach full size about six weeks after fertilization in early August.
Why Do Hazelnut Trees Need to Cross-Pollinate?
As mentioned earlier, hazelnut trees are self-incompatible. This means that a tree can’t set nuts with its own pollen. They need to receive pollen from a different hazelnut tree variety that is compatible. Additionally, some varieties are cross-incompatible, making pollination even more challenging.
The Importance of Pollinators
Hazelnuts are wind pollinated, so they rely on the wind to carry pollen from male to female flowers. However, wind pollination can be unreliable, especially in areas with little wind. To ensure successful pollination, it’s important to have compatible pollinizer trees nearby.
Pollination Management in Hazelnut Orchards
In hazelnut orchards, growers typically plant three pollinizer varieties (early, mid, and late season) throughout the orchard. This ensures that there is always a source of compatible pollen available during the pollination period. Pollinizer trees are usually placed every third tree in every third row.
Conclusion
Hazelnut pollination is a complex and fascinating process that requires a bit of help from the wind and compatible pollinizer trees. By understanding the unique pollination needs of hazelnuts, growers can optimize their orchards for successful nut production.
