Scientific name: Sphaeropteris excelsa
Plant type: Tree fern
Environment: Partial shade with moist, well-drained soil
Uses: Specimen plant
Ancient Plant Garden – 68F, 68B
Australia – 60B
Sphaeropteris excelsa, also known as the Norfolk tree fern or the smooth tree fern, is the tallest tree fern on Earth. Endemic to the Norfolk Islands in the South Pacific, Sphaeropteris excelsa is a member of the Cyatheaceae family.
Norfolk Island is a small island in the Pacific Ocean located between New Zealand and New Caledonia. The island was once covered by subtropical rainforests that were dominated by the Norfolk Island pine (Araucaria heterophylla), Norfolk Island palm (Rhopalostylis baueri), and the Norfolk tree fern. The island was uninhabited for hundreds of years before the late eighteenth century and this rainforest habitat made up most of the island’s landscape. The island was then sporadically populated until the mid-nineteenth century when settlers arrived from Pitcairn Island, a remote island in the South Pacific, and resettled Norfolk Island. These settlers began using the land for agriculture and would even use the stems of the smooth tree fern as food for livestock.
Today little of the rainforest habitat remains due to human activity and invasive plant species. What does remain of the subtropical rainforests has been protected as the Norfolk Island National Park and Botanic Garden, where the Norfolk tree fern can be found in moist gullies. Despite the small population, the Norfolk tree fern is rare but not considered endangered due to these conservation efforts and its availability commercially.
In the wild, Sphaeropteris excelsa can reach heights of over 60 ft and takes approximately 50 years to reach maturity. Giving it one of its common names, the trunk of S. excelsa becomes smooth over time, after fronds fall off leaving visible scars. Adding to the tree fern’s large presence, these fronds can grow up to 16 ft long. The Norfolk tree fern prefers moist, well-drained soil and partial shade.
Contributors: Text, profile, and photos by Victoria Stewart