The dell itself dates back to Kew's early days. Charles Bridgeman created a sunken garden in around 1734 and Capability Brown extended it in the 1770s. He named the feature Hollow Walk and planted it with mountain laurels. In 1847, the dell was replanted as a shrubbery.
At this time Sir Joseph Hooker travelled to the Himalayas on a plant-collecting mission. Kew’s annual report for 1850 records '21 baskets of Indian orchids and new species of rhododendrons' from Hooker. The rhododendrons were planted in sheltered parts of the Gardens, including in the dell.
Sir Joseph Hooker introduced 14 of the 25 rhododendron species described in Curtis’s Botanical Magazine between 1852 and 1856.
Hundreds of specimens now grow in the Rhododendron Dell, including some unique hybrids not found anywhere else.
Woodchip paths wind around specimens such as the pink-flowered Rhododendron myrtifolium, from the Carpathian and Balkan mountains, the highly-scented R. Kewense ‘King George’, and Kew’s oldest specimen, R. campanulatum.
The Rhododendron Dell is at its prime during April and May.