Plant Physiology Research

Genus Rhododendron as a model system for understanding the evolution of physiological adaptations to climate.

Rhododendrons are highly prized by gardeners for their beautiful floral displays, but few people know that there are 900+ species in the genus.

Rhododendrons are found in habitats range from hot to cold, from sunny to shady and from swampy to dry. Not only that, but thegenus includes ecologically important species known to significantly and permanently alter ecosystem function, endangered species with very specialized habitat associations, species that are currently increasing in dominance within their native habitat and others which are becoming aggressively invasive outside their natural habitats.


Rhododendron is an incredibly powerful system in which to address the evolution of physiological climate tolerance because the different habitats are associated with different traits, such as the variety of leaf types shown here. For example, there are evergreen species that tolerate cold stress and deciduous species that avoid it. In addition, the genus also includes semi-evergreen species that produce both deciduous leaves in the spring and cold-hardy evergreen leaves in the fall. This could represent a unique type of growth physiology, but almost nothing is known about the adaptive significance of the semi-evergreen habit.

The Holden Arboretum maintains an extensive Rhododendron collection, and continued study of this fascinating plant genus will provide unique insight into one of the most vital scientific questions of the current era: How do plants adapt to novel climates?