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Rhododendron illustration by Charles Faxon

Rhododendron Dell plants

Rhododendron 'Sir Charles Butler'
Rhododendron 'Sir Charles Butler'


Fun Facts

  • Native to China, Fortune's rhododendron (Rhododendron fortunei) was introduced to the west by British plant explorer Robert Fortune. This species and its multitude of crosses have large, heady-fragranced flowers in a range of colors. While most rhododendrons have five petals, this species typically has seven.

  • Native to North America, Catawba rosebay (Rhododendron catawbiense) have purple to lavender-pink colored flowers with yellow-brown blotch. The epithet catawbiense is derived from the Catawba River of North Carolina and South Carolina. Following the description of the species by French botanist André Michaux, plant breeders began crossing Catawba rosebay with other rhododendrons.

  • Today, hundreds of sun-loving, cold hardy cultivars available in nurseries have Catawba rosebay (Rhododendron catawbiense) in their parentage. The Arboretum’s ironclad rhododendrons are examples.

  • ‘Blue Peter’ (a cross of Rhododendron ponticum) flowers are held in a tight dome (truss) and are lavender-blue with a dark purple blotch. At the Arboretum, its habit is shrubby with flowers borne on erect stems.


Rhododendron Dell is a contemplative landscape showcasing the Arboretum’s core collection of hybrid and evergreen rhododendrons. An overstory of hemlock, birch, oak, maple, and pine provide ideal rhododendron habitat. In the early 1900s, Ernest Henry Wilson evaluated many of the rhododendrons in the collection and in 1917 published a list of “ironclads”—a group of hybrid rhododendrons that had proved hardy and floriferous at the Arnold Arboretum. Bred in the United Kingdom, these ironclads became the focus of regional plant introduction and breeding endeavors in New England. Many of the original ironclads, acquired in 1886 from the Woking Nursery in England, are the largest plants in the collection.

Today, rhododendron collections in Rhododendron Dell include 92 taxa (kinds). Of these, 72 are cultivars which have been selected for horticultural merits including flower color and fragrance, truss (domed flower mass) size, leaf morphology, and hardiness.



Plants in this Collection

Plant ID Accession Date Received As Origin Source

Featured Walk

This quarter-mile tour through the Explorers Garden features stories from the Arboretum’s century and a half of collecting plants around the world. If you’re at the Arboretum, click here to take a version of this tour with Expeditions, our mobile web app.

Dove tree (Davidia involucrata)

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