Geography and distribution
Mellissia begoniifolia occurs only on St Helena in the South Atlantic Ocean. According to a record from 1813, St Helena boxwood used to be abundant on Boxwood Hill, which bears its name, and on other hills in the dry south and south-eastern side of the island.
Monitoring the last surviving adult wild specimen of St Helena boxwood.
After declining and apparently going extinct for many years, a small population of St Helena boxwood was rediscovered in November 1998 in the south-western part of the island, on a sea-facing slope below Lot’s Wife, about 100 m above sea level.
Overview: St Helena boxwood is a branching shrub that can grow up to 2.5 m, with a pungent smell, reminiscent of ‘smelly feet’, or tobacco, to which it is distantly related. Its trunk and older stems have reddish-brown bark, with vertical green stripes. The reproductive shoots have zig-zag stems bearing paired leaves.
Leaves: Are broad and rounded at the base, tapering at the tip, and are leathery or fleshy with a slightly sticky surface. As the plant grows older, it produces smaller leaves.
Flowers: It blooms between October and December with solitary drooping white flowers (about 5 mm wide) between pairs of leaves.
Fruits: The fruit, which is a conical berry, is brown and dry when mature, and contains up to 40 seeds.
Threats and conservation
Kew’s horticulturists use a fine paintbrush to transfer pollen between flowers.
When it was last assessed for the IUCN Red List in 2003, St Helena boxwood was categorised as Critically Endangered. By 2010, the last surviving plants on St Helena had drastically declined in number, to only one adult, which was under extreme stress caused by drought and pest infestation (including aphids, whitefly and root mealy bugs). Although this adult plant has now died, some seedlings have emerged from seeds present in the soil following the recent rains. However, it is by no means certain that these will survive long enough to reach flowering size. As there are currently no adult flowering plants, this species is now considered to be effectively extinct in the wild.
Invasive animal species, such as rabbits and goats, have also been known to graze on this species; however, its pungent smell (possibly due to toxic chemicals within the plant) may have reduced grazing damage. Other natural threats include soil erosion, drought, and plants being crushed by shifting rocks.
In order to conserve this species, seeds collected from the island’s last surviving boxwood plants have been germinated at Kew and are now being grown on by horticulturists here, in preparation for re-introduction on St Helena, with the goal of eventually restoring the whole habitat. The plants grown at Kew from the original seeds are pollinated by hand, and over 13,000 seeds have been collected from these cultivated plants in just a few months. Some of these seeds have been sent to Kew's Millennium Seed Bank (MSB) for storage. Batches of seed are being sent back to St Helena, where they are being germinated and returned to their natural habitat as small plants. Some experimentation with direct seed sowing is being tried. Plants have also been established in several other areas on St Helena where M. begoniifolia was known to grow, but has since been lost.
Dry branches of St Helena boxwood were used by the islanders as firewood. Mellissia begoniifolia is closely related to Withania species, which have medicinal properties, and research is underway to find out whether St Helena boxwood is also of potential medicinal value.
Millennium Seed Bank: Seed storage
Kew's Millennium Seed Bank Partnership aims to save plant life world wide, focusing on plants under threat and those of most use in the future. Seeds are dried, packaged and stored at a sub-zero temperature in our seed bank vault.
Description of seeds: The seeds of Mellissia begoniifolia are approximately 1 x 0.5 mm, pitted, round and black. One thousand seeds weigh approximately 0.8 g.
Number of seed collections stored in the Millennium Seed Bank: Eight collections, totalling over 50,000 seeds.
Germination testing: At regular intervals, germination tests are carried out using small batches of seed to check that they are still viable and to estimate the seeds’ overall storage life. St Helena boxwood seeds should cope well with being dried, since plants have to go through long periods of drought on the island. During the drought, seeds can remain dormant in the soil until the wetter months, when they can germinate safely.
Kew's James Beattie transfers pollen between flowers.
St Helena boxwood is grown in a warm glasshouse at Kew to mimic its natural subtropical conditions. Cultivation from seed has been more successful than from cuttings. The plants can be susceptible to insect pests, which are controlled using a combination of insect parasites and occasional pesticide sprays (integrated pest management) at Kew. Pinguicula moranensis, a carnivorous plant which traps pests on its sticky leaves, is grown adjacent to the boxwood plants, to monitor and control pest levels.
Kew’s horticultural staff have been developing methods of propagating a number of St Helena’s unique species for more than 20 years, both from seed and from cuttings.
St Helena boxwood at Kew
A living specimen of St Helena boxwood can be seen in Kew’s Temperate House in the island floras bed, alongside some of the island’s other unique species.
This herbarium specimen of St Helena boxwood is one of the 336 plant specimens from St Helena held in Kew's Herbarium.
The genus Mellissia was named in honour of John Melliss, who collected Kew's herbarium specimen (right) and made the notes about it. Melliss was born on St Helena in 1835 and trained as an engineer. He acted as the surveyor-general on the island from 1860 to 1871. In 1875, he published the book St. Helena: A Physical, Historical and Topographical Description of the Island, including the Geology, Fauna, Flora and Meteorology.
Kew's conservation work on St Helena
Kew has been involved in conservation projects on St Helena for over 30 years. As well as supporting the islanders in cataloguing the plant species found there, both native and introduced, Kew staff have helped to develop the horticultural facilities and skills needed to propagate native plants for reintroduction to the wild.
‘Supporting Critical Species Recovery and Horticultural Needs on St Helena’ is a joint Kew - St Helena Government (Agriculture and Natural Resources Department) project funded by the Overseas Territories Environment Programme (OTEP).
Through this project many highly threatened St Helena endemics, including Mellissia begoniifolia, are currently being propagated at the Government Nursery as part of a major conservation effort. Large numbers of plants are being re-introduced to the wild in an attempt to re-establish viable populations of these species.
In addition the habitat is being conditioned in a restoration effort to try and maximise the chances of success.