Witch Hazel’s Secrets

Written By: Winter Gary | Issue: 2021/11 – November

For over 50 years, the Highlands Biological Foundation has provided Grants-in-Aid of Research at the Highlands Biological Station, bringing graduate students and research scientists to Highlands from all over the country and abroad. 

This summer, Justin Jorge, a PhD student from Duke University and one of the Foundation’s 2021 GIA recipients, has been working on a captivating project using high speed cameras to record the “ballistic firing” of Witch Hazel (Hamamelis virginiana) seeds.

Walking by a Witch Hazel plant in the fall, you run the risk of getting shot by a seed. Like other seed shooting plants, the witch hazel launches its seeds by slowly loading energy into a spring-like material that later recoils, expelling the seed like an arrow shot from a bow. In the Witch Hazel, the spring is a hard structure that surrounds each seed called the endocarp which deforms as the fruit dries. At a critical point, the endocarp recoils and rapidly pinches on the seed, shooting it out at velocities of up to 12 meters per second (about 26.8 miles per hour). 

Jorge is studying Witch Hazels to probe a tradeoff that affects all seed shooting plants: the tradeoff between seed size and seed ejection velocity. Larger springs may store more energy, increasing ejection velocity. Larger, heavier seeds decrease ejection velocity but may contain more provisions for the embryo. Therefore, the interplay between seed mass and endocarp mass affects ejection velocity, and potentially dispersal distance. 

Jorge is currently collecting data from Witch Hazel fruits around HBS to investigate if the environment where the plant developed affects the ratio of seed mass to endocarp mass. 

HBS’s Associate Director, Jason Love, notes that Jorge’s work, “helps highlight the breadth of research that takes place at the Station – there is more to HBS than just salamanders and plant surveys. His research in biomechanics of witch hazel seed dispersal may provide insights on not only how evolution has created an efficient method for dispersing seeds, but may yield insights into how we can copy such a design for other uses.”

The research funded by the Foundation’s GIA program contributes to a better understanding of the incredible biodiversity of this region. Our GIA program has yielded hundreds of graduate theses and thousands of scientific papers.    

For more information about our GIAs or other efforts that the Foundation supports at HBS, visit highlandsbiological.org. HBS is a multi-campus center of Western Carolina University.