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The Trochetiopsis Gallery
Trochetiopsis is a genus of 3 species (and 1 hybrid) of Malvaceous shrubs or small trees, endemic to the South Atlantic island of St. Helena. All species are extinct or nearly so in the wild, but are present in cultivation.
Trochetiopsis is part of the core of the Dombeyoideae sub-family of Malvaceae, related to taxa from Africa, Madagascar and the Mascarene islands such as Dombeya, Trochetia, Helmiopsis and Ruizia. The genus was erected in 1981, by W. Marais, to include T. melanoxylon and T. erythroxylon. Previously these species had been placed in a variety of Dombeyoid genera. (See synonymy.) Q.C.B. Cronk separated T. ebenus from T. melanoxylon in 1995, and at the same time described the hybrid between T. ebenus and T. erythroxylon as T. × benjaminii
Trochetiopsis erythroxylon (Forst.f.)
St. Helena Redwood
The St. Helena Redwood, T. erythroxylon, is a small tree. It used to grow to 6m in height, but due to the adverse effects of inbreeding it now only reaches 3m. The bark is an even dark brown in colour, and relatively smooth in texture. The foliage is alternate, petiolate and stipulate. The stipules are awl-shaped. The ovate leaves are pale green, about 3" long, and 2" or more wide. They are 35-nerved, cordate at the base, with crenulate margins, and acuminate at the apex. The upper surface is smooth. The lower surface is reticulate, and hoary when young. Older leaves quickly turn yellow and speckled, before falling. It flowers primarily in late spring, but flowers can be produced at any time of year. They are borne on solitary axillary peduncles, with two or three flowers on each peduncle. The peduncles are about the same length as the leaf petioles. The flowers are trumpet shaped, about 2" across, and 3" long, and are borne pendantly. They open pure white, but age first to pink, and finally to a deep red. The flowers have 5 stamens, and also five flesh-coloured staminodes. The style is about twice the length of the stamens. The fruits are oblong, pointed, hairy, capsules with 3 to 5 seeds in each cell. The calyx is persistent, and in fruit exceeds the capsule in length,
The St. Helena Redwood was an emergent in and a major constituent of the Cabbage Tree Woodland zone of the moister upland regions of St. Helena, between the heights of 500m and 650m, above the Gumwood zone, and below the tree palm zone. It was exploited for its wood, which provided a close-grained, mahogany-coloured, hard, durable timber, and its bark (using for tanning cattle hides), and also suffered from the depredations of imported goats, and was very rare by 1718. It is now extinct in the wild; the last wild tree having died in the 1950s. Selfed seedlings of this tree were planted in a number of locations. These trees display the effects on inbreeding depression, often being dwarfed or misshapen. Cross-pollinated seedlings were planted in 1997, and it is hoped that these will show healthier growth.
Trochetiopsis ebenus Q.C.B. Cronk
St. Helena Ebony
The St. Helena Ebony, T. ebenus, is a low spreading shrub with horizontal stems, although it used to grow to 4m in height. The leaves are ovate and sub-cordate, with acute or rounded ends. They are approximately 3" long, and perhaps half that in width. They are dark green in colour, with brown hairs on the buff coloured underside.
The flowers are mostly borne in summer, but can occur at any time of the year. They are about 3" in diameter, opening white, and aging to pink, before forming a seed pod. (All flowers that I have seen have been white or nearly so.) They have an epicalyx composed of 3 short triangular segments. They have a short dark reddish purplish brown staminal column, on which are borne 5 ligulate staminodes of the same colour, surrounded by 5 stamens. The filaments and pollen of the stamens are orange. The style is white. It has five ligulate arms, which are initial curled together to form a club shaped head, but which separate to form a star.
It was once abundant in the western parts of St. Helena, in dryer areas between 200m and 500m in altitude. It suffered greatly from the depredations of goats, and was nearly extinct by 1771. It was assumed to be extinct in 1850, but two bushes were rediscovered in 1980. From this many thousands of specimens have been propagated by seed and vegative propagation. These represent a small, and perhaps atypical, representation of the former variability of the species.
However they are readily propagated from cuttings, and are now present in the horticultural trade as a tender shrub.
Trochetiopsis melanoxylon (R.Brown ex
Aiton f.) W. Marais
St. Helena Dwarf Ebony
St. Helena Blackwood
T. melanoxylon was not distinguished from T. ebenus until 1995, both species being subsumed under the former name until then. Confusion between the two species remains in some of the literature.
T. melanoxylon was a dwarf shrub growing at low altitudes in the arid rain shadow areas north of the central ridge. The bark of old wood is rather rough, and dark olive-black in colour. The foliage is alternate, long-petiolate and stipulate. The stipules are awl-shaped. The ovate leaves are 3-nerved, cordate at the base, with subentire margins. The are smooth above, and covered with a ferruginous stellate indumentum beneath. This indumentum is shared with the young shoots, petioles, peduncles, bracteoles and calyx. The flowers are large and campanulate, opening white and becoming pink or rosy as they age. They are borne on solitary, axillary peduncles, with one or two flowers borne on each peduncle. They are involucellate, the three bracteoles being ovate-lanceolate, and closely appressed to the calyx. There are 5 stamens, and 5 dark purple, club-shaped, staminodes. The fruit is an ovate, obtuse, capsule, with two or three seeds in each cell. It is much shorter than the persistent calyx.
Due the confusion between T. melanoxylon and T. ebenus the status of T. melanoxylon is not wholly clear to me, but it would appear that T. melanoxylon is extinct, not having been recorded since 1771, and that plants in cultivation under this name are T. ebenus.
Trochetiopsis × benjamini Q.C.B. Cronk
A hybrid between T. ebenus and T. erythroxylon. This is an extremely vigorous plant, and may provide the only chance of survival for the T. erythroxylon gene pool.
© 2003 Stewart Robert Hinsley