25 February 2021

Saint Helena’s rarest plants growing at Kew

False gumwood (Commidendrum spurium) and bastard gumwood (Commidendrum rotundifolium) are now growing in our Tropical Nursery.

By Thomas Pickering

Aerial view of Saint Helena island

The first human eyes which looked upon the island of Saint Helena would have seen something very different from its landscape today.

The island is exceptionally isolated, more than 1,200 miles from the nearest landmass, emerging from the ocean along the Mid-Atlantic Ridge.

Its landscape is rugged, rocky and windswept with dry, warm coastal areas.

The climate is relatively temperate and consistent in nature, being swept by the southeast trade wind.

Saint Helena rises steeply from sea level to mist-covered peaks which are just over 800 metres above sea level.

False gumwood (Commidendrum spurium) in our Tropical Nursery
False gumwood (Commidendrum spurium) in our Tropical Nursery © RBG Kew

The Portuguese discovered the island uninhabited, with an abundance of strange trees and water.

It quickly became an important stop for the Portuguese on their return trade route from India. It wasn't long before the island was influenced by the significant introductions of goats, pigs, rats and a host of plants including fruit trees.

The landscape was quickly affected by the removal of resources from the land.

Later, the island became known to the British and became an important strategic outpost for them.

In 1657, Oliver Cromwell granted the East India Company the authority to govern the island and within three years Saint Helena was colonised with settlers and a governor.

The human impact on Saint Helena through the subsequent centuries has been dramatic.

Deforestation, soil erosion and the introduction of invasive plants and animals has ravaged the pre-human inhabitants of the island and driven many extinction events as a result.

Now, only fragments of the native Scrubwood forests remain with island endemics clinging to inaccessible cliffs and pockets of vegetation.

In some cases, species are represented by only a handful of remaining individuals. 

Bastard gumwood (Commidendrum rotundifolium)
Bastard gumwood (Commidendrum rotundifolium) © Tim Adriaens/Wikimedia Commons

In our Tropical Nursery here at Kew, two of Saint Helena’s Critically Endangered (IUCN) endemic plant species have been successfully grown from seed and reintroduced to the Living Collections alongside other endemics from the island.

False gumwood (Commidendrum spurium) and bastard gumwood (Commidendrum rotundifolium) both lead precarious existences on their native island home and represent the last fragments of once more prosperous species.

Commidendrum spurium is now thought to have a wild population of just six individuals confined to a single rocky outcrop.

Commidendrum rotundifolium is represented by a single wild individual which grows from a crack in a cliff, a drop of over 50 metres below it.

In the Tropical Nursery we have succeeded in germinating and growing these two species from seed collections stored in our Millennium Seed Bank at Wakehurst.   

False gumwood (Commidendrum spurium) illustration
False gumwood (Commidendrum spurium) illustration © RBG Kew
False gumwood (Commidendrum spurium) illustration
False gumwood (Commidendrum spurium) illustration © RBG Kew

In order to ensure the best chances for these plants in cultivation, our Tropical Nursery staff will maintain optimum diversity within the ex-situ plants, as well as the subsequent seed collected from these individuals through careful clonal propagation methods and controlled cross-pollination.

A key priority will be to share and distribute these plants to other botanic gardens to ensure the survival of these unique plants.

Further work is underway to obtain seeds from other Saint Helena endemics not represented in our Living Collections so we can continue to support conservation work for the island.

It's exciting to see how our expertise can restore and protect these endangered species. 

Tom Pickering is Nursery Supervisor in the Tropical Nursery at Kew.

Callistemon citrinus,  the bottlebrush plant

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