Endemics of St Helena - Gumwood

 

GUMWOOD

 

 

Common name: Gumwood

Scientific name: Commidendrum robustum

IUCN status: Endangered

 

 

Natural History

Gumwood woodland once stretched across one third of the Island, along the mid-altitude zone from 400-600m. This woodland was quickly reduced in size due at first to goats and later collection for firewood, timber and continued grazing of stock. Today almost all of the gumwood woods have been destroyed. Examples where gumwoods once grew are: Deadwood, Bottom Woods, Longwood, Woody Ridge, Gumwoods, Levelwood, Woodlands, Peak Dale, Thompson's Wood and Half Tree Hollow.

The only example of gumwood woods now left on the Island is that at Peak Dale, between Peak Dale Cottage and Old Luffkins. Smaller scattered populations of gumwoods can also be found at Deep Valley, Rock Rose, Longwood, Thompson's Wood and Marias. Most are found growing close to or actually growing out of the cliffs. Surviving extinction because of the awkward position in which they grow.

In 1977 the gumwood was adopted as St Helena's National Tree. In 1991 the Peak Dale gumwoods were attacked by the Jacaranda bug (Orthezia insignis). The Jacaranda bug which looks a little like a whitefly is a sucking insect that takes the sap from the tree. A black sooty mould covers the branches attracted by the honey dew produced by the Jacaranda bugs. The whole population at Peak Dale looked likely to be lost as the jacaranda swept through the population killing hundreds of trees. Fortunately for the gumwood and for St Helena, a biological control agent, a ladybird (Hyperaspis pantherina) introduced from Kenya brought the infestation under control. Although the Island will never be free of the Jacaranda bug it will at least be kept from causing such widespread damage as it did between 1991 and 1994.

DESCRIPTION

Gumwoods grow to a height of about 8 metres. They have a highly branching structure, forking low and producing an umbrella like canopy. The leaves are between 7 and 10 cm long and varyf rom grey green to dark green. They are thick and hairy giving a wrinkled impression and are borne in tight whorls. Flower heads droop down from the ends of the branches and are white. They are usually borne in the winter and spring months. Seeds germinate freely to produce a carpet of seedlings under the canopy of the parent plants. However since the attack of the Jacaranda bug in 1991 few seedlings have survived in the wild.

Unpublished work by Quentin Cronk suggestes that the Peak Dale gumwoods are a relatively recent hybrid population. The variation between the trees in leaf form and colour is clear to see. Seedlings from Peak Dale have been used in all the plantings across the Island. It is likey that the trees at Deep Valley and Longwood are different from the Peak Dale trees.

NUMBER OF SURVIVING POPULATIONS

The only gumwood wood left is that at Peak Dale. Here over 500 trees are growing on the steep slopes covering an area of about 3 hectares. Other wild surviving populations are at: Marias, towards Fairyland where two small populations of 7 and 12 individuals survive; Deep Valley where 21 trees are growing close to or on cliffs above the valley; Rock Rose where 7 trees grow on a cliff surrounded by buddleia, and ginger; a single tree still survives at Thompson's Wood and up to 3 at Devils Hole. Perhaps the most easily recognised gumwoods are those at Longwood, where four trees are growing along the strip of land between the golf course or Piccolo and Bilberry Field. Although these are some of the oldest gumwoods to be found on the Island these were probably planted.

CONSERVATION RECOVERY PROGRAMMES

There has been a long running gumwood replanting programme on Horse Point Plain. This planting was started in 1988 by Norman Williams and developed by George Benjamin. It has been remarkable in its success with hundreds of gumwoods now successfully established. Remarkable considering the harsh nature of the environment: dry and windswept. Gumwoods have also been established behind High Peak, at Pounceys, along the Golf course and in the grounds of many of the Island's first and middle schools.

Recently attention has returned to the wild populations which have either been attacked by the Jacaranda bug or heavily invaded with alien plant species such as flax, ink, bilberry, black olive or both. Clearance of weeds at three sites has now been completed and replanting of gumwoods to restock these ailing populations is underway. Seed has been collected across all the different populations over the last year. Seedlings are growing in the nursery ready to be planted back in the different sites.