Bastard Gumwood

Commidendrum rotundifolium

Family: Asteraceae

Natural Range: St Helena Island

IUCN Conservation Status

Critically Endangered (CR)

The bastard gumwood (Commidendrum rotundifolium) is endemic to St Helena, a small island in the South Atlantic. This volcanic island has 45 reported endemic plant species, however all of them are rare and threatened and at least 8 are thought to already be extinct. Conservation efforts have been trying to save the bastard gumwood from extinction and the future is now looking brighter for this tree species.

By the end of the 19th Century, the bastard gumwood was thought to be extinct until an individual tree was rediscovered in 1982 on a remote cliff. This tree was then destroyed by a gale in 1986 and the species was assessed as Extinct in the Wild on the IUCN Red List.

Since this assessment, another single wild individual tree has been discovered, which grows out from a crack in a cliff with a drop of over 50m below it. There is also one remaining mature cultivated individual.

bg at botleys St Helena. A.darlow

The only wild individual of Commidendrum rotundifolium growing out of a cliff on St Helena Island. Credit; Philip Lambdon

The bastard gumwood and the now extinct Helena ebony tree (Trochetiopsis melanoxylon) are dryland species. These species once formed dry forests which covered the mid-altitude zone of the island. When the British colonized the island in 1600 these forests were cleared for timber and plantations. Remaining trees were threatened from overgrazing by introduced mammals such as pigs and goats as well as competition from highly invasive plant species.

Conservation projects on the island are working to establish a self-sustaining population of the bastard gumwood. The tree is enclosed in a cage of netting to prevent cross pollination by insects from its sister species the false gumwood (Commidendrum spurium).

To produce fertile seeds from which to grow new seedlings the tree must be self-pollinated and this must be done by hand. Small paintbrushes are used to collect pollen grains and spread them from one flower to another. However, this is made more difficult by the fact the tree has mechanisms in place to prevent self-pollination. Only 1 in 10,000 pollen grains have the genetic mutation which will allow self-pollination to occur.

BG flower. Taken by T.Heller/RBG Kew

Commidendrum rotundifolium flower. Photo taken by T.Heller/RBG Kew

Since 2010, almost 500 saplings have successfully been grown. These young trees are planted away from other gumwoods and were able to be pollinated naturally by insects.  These trees originally planted have since gone on to produce natural offspring and more saplings have been planted including alongside other dryland species in a protected area to try to restore dry forest communities.The success in planting new saplings and increasing the number of ex situ individuals as well as the discovery of a mature individual in the wild means the future of the bastard gumwood is looking much more hopeful.

Did you know?

The Global Trees Campaign has supported tree conservation in over 25 countries, implementing conservation projects for over 100 threatened tree species.