Pacific Plant Promotions: Trochetiopsis ebenus

By: Kathy Musial

Kathy Musial is curator of living collections at the Huntington Botanical Gardens where she has worked for more than twenty-five…

More From This Author
Flower of Trochetiopsis ebenus. Photograph by Dylan Hannon

Flower of Trochetiopsis ebenus. Photograph by Dylan Hannon

St Helena is one of those faraway, exotic countries that I first learned about through stamp-collecting as a child. Others may have heard of St Helena in history class, as the exiled home of Napoleon Bonaparte following his defeat at Waterloo. During my years at the Huntington, I have come to know St Helena as the natural home of many interesting and endangered plants. One of these, Trochetiopsis ebenus, is our current Pacific Plant Promotions offering.

St Helena is an isolated oceanic island of volcanic origin, about forty-seven square miles in size and 2,685 feet elevation at its highest point. Its location at 16° south latitude in the Atlantic Ocean gives it a tropical to subtropical climate. Discovered by Portuguese navigators in 1502 and later colonized by the British, its vegetation has unfortunately succumbed to the overgrazing and overharvesting that have befallen so many other islands. Though early accounts describe the island as completely vegetated, today it is mostly barren and overtaken by alien plants, and nine of its forty endemic species are extinct. Isolated and inaccessible ridges and cliffs remain as the only refuge for much of the surviving flora.

Trochetiopsis was segregated from Trochetia in 1981, and its three species are confined to St Helena. (The six species of Trochetia are found on Mauritius and Reunion islands.) Members of both genera are small woody trees and shrubs with attractive bell-shaped flowers, placed by taxonomists in the same family (Sterculiaceae) with flannel bush (Fremontodendron spp.) and Dombeya spp. Of the three species of Trochetiopsis, T. melanoxylon is now extinct, T. erythroxylon is extinct in the wild and known only in cultivation, and T. ebenus exists in the wild as only two specimens. When these two individuals were discovered in 1980, they were thought to be the extinct T. melanoxylon. Further study revealed them to be a third, at that time undescribed, species (T. ebenus); all three have a convoluted taxonomic history, which adds to the confusion. Trochetiopsis ebenus was formally described in 1995 and is now the correct botanical name for what had been known as the St Helena ebony, assumed to be extinct as of 1850—until this recent discovery. Its common name, St Helena ebony, had erroneously been attributed to T. melanoxylon, last seen alive prior to 1800 and now known only in herbarium specimens; this species had been found in the more arid, northern coastal lowlands. Trochetiopsis ebenus was once abundant in the dry, rocky, mid-elevation, southwestern part of the island.

Foliage of Trochetiopsis ebenus, showing the bronze hairs on leaves and stems. Author’s photograph

Foliage of Trochetiopsis ebenus, showing the bronze hairs on leaves and stems. Author’s photograph

The existing wild plants of Trochetiopsis ebenus (and their subsequent progeny) are small dome-shaped shrubs, though records show that this species once grew to tree size, typically fifteen to eighteen feet tall. The extant “species” therefore is not truly representative, but is an ecotype. Nevertheless, they are attractive, rounded shrubs to about three or four feet high and as wide. The three-inch, long-petioled leaves are lanceolate with a cordate base, somewhat leathery, and mid-green on the upper surface. Bronzy hairs cover the new growth, lower leaf surfaces, petioles, and stems. The flowers are in pairs, with white, crepe-like, flaring petals. Flowering occurs during summer, though in some years, our plants have been shy bloomers. Even without flowers, the bronze coloring of leaves and stems makes it a handsome foliage plant, its size and shape suited to both container and garden culture.

After its rediscovery in 1980, cuttings were brought to the Cambridge Botanic Garden and later distributed to other gardens. These cultivated plants have produced seeds that have been further distributed. Similarly, cuttings from the two wild plants were grown in St Helena to establish seed-producing parent plants. From these, at least 2,000 seedlings have been grown, many of which have been reintroduced into several wild localities on the island. In 1985, the Huntington received one plant each of Trochetiopsis erythroxylon and T. ebenus (then still known as T. melanoxylon) from the San Diego Zoological Gardens. These were planted in the garden in 1988, but, sadly, both succumbed to the 1990 freeze.

In 1993, we received seeds of Trochetiopsis ebenus (again under the name T. melanoxylon). Enough of these germinated that we were able to distribute the extra plants to other botanical gardens. Of this crop, three were planted in 1996 in a sunny area of the Subtropical Garden, where they are watered weekly.

Trochetiopsis ebenus is frost tender and requires some winter protection; in colder areas, grow it in a greenhouse or container that can be brought into a well-protected place for the winter. Give average water and occasional fertilizer during the warmer growing season, less in winter. No pruning or other special care is needed.

Trochetiopsis ebenus may now begin to join the ranks of such plants as parrot’s beak (Lotus berthelotii), Franklinia alatamaha, and African violet (Saintpaulia ionantha) that are extinct, or nearly so, in the wild but well-established in cultivation.

The Huntington Botanical Gardens will be offering cutting-grown plants of Trochetiopsis ebenus, as part of the continuing Pacific Plant Promotions. See Pacific Horticulture, January 2000, for a description of the program. To order a plant of Trochetiopsis ebenus, see the PPP reservation card (opposite page 64) for details.