Hazelnuts, also known as filberts and cobnuts, begin to ripen as hazel tree leaves change color. Most ripe nuts are found in September and October, depending on the weather.
Hazelnuts thrive in regions of mild, moist winters combined with cool summers, and produce nuts around 4 years of age but don’t really become productive until closer to 7 years of age. Clusters of blossoms appear in the late winter to early spring between February and March. Once the flowers are pollinated, nuts begin to form. Over the course of the summer months, the nuts continue to mature leading up to the harvesting of hazelnuts in October. Once the nuts have been harvested, the tree will become dormant until the next spring.