St Helena olive (Nesiota elliptica)
|Size||Height: up to 4m (2)|
Leaf length: 5 - 8 cm (2)
Leaf width: 2 - 3.5 cm (2)
Classified as Extinct (EX) by the IUCN Red List (1).
In 2002, the St Helena olive had been lost from the wild and persisted only precariously, as one cultivated individual (3), but since then this individual has died, making this species totally extinct (1). This olive was a relatively low and spreading tree with numerous branches and dark brown to black bark (2). The dark green leaves were oblong in shape with curved tips; they had a pale underside with flat-lying hairs (2). The inflorescence (flower stalk) was branched and did not rise above the leaves; in season it bore numerous, tightly packed pale pink flowers (2). The fruits were hard, woody capsules measuring one to two centimetres long, they split when mature revealing the triangular, shiny black seeds inside (2).
Endemic to the remote island of St Helena in the southern Atlantic Ocean, this species became very rare in the 19th Century (2). It was then believed to be extinct until a single tree was found in 1977; with the death of this specimen in 1994, however, the species was lost from the wild (2). Despite tenacious attempts to cultivate cuttings from this plant, success was limited and in 2004 the St Helena olive went extinct (1).
Formerly found on the highest points of the eastern central ridge (2).
Little is known about the natural ecology of the St Helena olive, but the flowering time was reported to be June to October. It is thought that pollination occured through the endemic fly Loveridgeana beattiei, and that fruits take a year to mature (2). The tree is 99 percent self-incompatible, and so could not set seed with itself or closely related individuals (7).
The remote island of St Helena was once home to a stunning array of endemic flora and fauna, which have developed there in isolation (4). Humans have exploited the island's resources for over 450 years, destroying much of the native vegetation through deforestation for timber and agriculture, and the grazing of introduced goats (4). The self-incompatibility presented serious problems for a tree confined to such a small area as the population size has been limited throughout history (7).
Although seedlings have proven extremely difficult to cultivate (5), a single successful cutting was grown from the last wild tree that died in 1994. The Endemic Plant Propagation Unit at Scotland, now known as the Environmental Conservation Section, St Helena raised this cutting to a two metre tall tree, however, this was sadly lost in 1997 (6). Two seedlings from this tree were raised and planted out in the Conservation Officer’s garden at Pounceys (160 and 80 centimetres high in 1995) (3). A third seedling was planted out near to the main plant at Scotland but was later transplanted into an area on the Peaks, when the cutting died and its own growth was also severely impeded (3). A fourth seedling raised from the cutting in Scotland was planted beside the third seedling on the Peaks (3). The health of the smaller olive at Pounceys and the two on the Peaks declined and they were all dead by 1999. Only the larger seedling survived at Pounceys and, like the others, showed signs of ill health due to fungal infections (3). It finally died in 2004, leaving the species extinct (1).
For more information on St Helena see:
- St Helena National Trust:
- UK Overseas Territories Conservation Forum (UKOTCF):
Authenticated (30/6/03) by Rebecca Cairns-Wicks. Chair, IUCN SSC South Atlantic Island Plant Specialist Group.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Inflorescence: the reproductive shoot of the plant, which bears flowers (See http://www.rbgkew.org.uk/ksheets/pdfs/flower.pdf for a fact sheet on flower structure).
IUCN Red List (December, 2009)