This Tree is up to 6m high. Leaves are simple. The zygomorphic, bisexual Flowers are in racemes. The Fruit is an explosive dehiscent capsule. Seeds have 1 or more ridges.
Duvernoia adhatodoides, Adhatoda duvernoia
RSA Tree No. 681.
Common names: Pistol Bush.
Family: Acanthaceae (The acanthus family). This family has about 230 genera and 4 000 species. In southern Africa, there are about 42 genera and 350 species. All members have simple Leaves without stipules. They are mostly entire. Inflorescences are mostly bracteate – subtending each flower. The Flowers are usually zygomorphic, bisexual with a nectariferous disc. The calyx usually shorter than the gamopetalous corolla, which has 1-2 lips. Usually 4 Stamens arising on the corolla are present. The 2-locular Ovary is superior and contains a large embryo. Fruit is 2-locular and Seeds lack endosperm. Local Tree genera include Barleria, Duvernoia and Mackaya.
Name derivation: This plant was first collected near Umtata. Duvernoia – named after Johann Georg Duvernoy (1692-1759) a German Botanist and professor of anatomy. He wrote the book, “Designatio plantarum circa Tubingensem arcem florentium”. The book is about the native flora in Tubingen (university town – south of Stuttgart). adhatodoides – resembles Adhatoda a genus in the same family. There are 2 species in the genus Duvernoia in southern Africa. The other is Duvernoia aconitfolia.
Conservation Status: L C. (Least Concern). Assessment Date: 2009.
Description. This Tree is usually small – between 3 and 6m high. It is often a sturdy, a multi-stemmed, shrub and has a trunk that may reach 26cm in diameter. The Bark is brown, rough and fissured. Longitudinal, orange Lenticels (a usually raised corky oval or elongated area on the plant that allows the uncontrolled interchange of gases with the environment) are visible (photo 576). Young branches may be pinkish and flattened at nodes. The velvety branchlets are almost square to grooved and brittle. They are often glandular. New growth is dark blue/green (photo 976).
This evergreen plant has large, simple Leaves that are glossy green above and lighter below. They are opposite or almost so and are more or less oval to lanceolate or even elliptic. Leaves are firm to the touch and up to 23 x 15cm. The Midrib is prominent on both surfaces – slightly sunken above but both the midrib and lateral veins protrude below and here the smaller veins are raised and visible. Veins are best seen against a strong light with a hand lens (Photos 697 and 643). The Apex nay taper broadly or abruptly. Petiole (leaf stalk) is up to about 2cm long. The Base tapers and is Decurrent (leaf blades that partly wraps or has wings around the petiole (photo 733). Here it may curve down and partly surround the upper part of the petiole. The Margin is entire, and may be wavy and rolled under – particularly next to the petiole.
These impressive bisexual, orchid-like Flowers appear in threes in late summer and may be scented. They are zygomorphic (irregular flower: when corolla is divisible into 2 equal halves in one plane only). Buds are shell like and slightly curved. Flowers occur in the axils of upper leaves in closely packed racemes (a simple elongated inflorescence with stalked flowers). Individual flowers have pedicels (stalk of a single flower) that are up to 8cm long. Bracts (much-reduced leaf, particularly the small scale-like leaves in a flower cluster or associated with flowers) are leaf-like and occur between the flowers. They are oblanceolate (broader at the apical third than at the middle and tapering towards the base), up to 2cm long and persistent. The bell-shaped Calyx has 5 pointed lobes. A tube is present and is longer than the attached lobes. The Corolla tube ends with a 2-lipped opening with 5 unequal lobes. The upper lip has 2 short lobes and appears hooded. The lower lip is 3-lobed with the tube that is shorter than the lobes. The wider centre lobe is noticeably marked with 5 purple almost parallel lines and dots which appear mainly outside the lines in the throat. These dots are also visible on the remaining 2 lower lobes. Staminodes (sterile stamens) are absent. There are 2 fertile exserted (projecting beyond, as stamens from a perianth) Stamens that arise in the mouth of the corolla and extending beyond. The Filaments are terete (circular in cross section). The Anthers each have 2 parallel thecae (pollen sacs) and the tiny pollen grains are shaped like rugby balls. The superior Ovary is densely hairy and has 2 ovules in each Locule. The terete Style runs in rugula (a small fold) and has 2 short, equal branches. (Feb-Aug). Carpenter bees pollinate the Flowers.
The club-shaped Fruit is a hairy Capsule about 3 x 1cm. It is initially green and turns brown when mature. It dehisces (the method or process of opening a seedpod or an anther), rupturing explosively with a loud crack, throwing the seeds some distance (Feb-Oct). Several disc-like Seeds develop, each about 5mm in diameter. They contain at least one ridge and have rough projections (photo 250).
Distribution & Ecology
This Plant is often an undershrub within a forest and located on rocky outcrops up to 1 900m. It also occurs along streams on forest margins. Trees are located in the Eastern Cape, KwaZulu-Natal, Gauteng, Mpumalanga and in Swaziland. They are not naturally part of the Western Cape.
This Plant is slightly frost sensitive. It makes a useful hedge. The Heartwood is dense, yellow and close grained with an attractive finish. It is easily Grown from cuttings or seeds. It is fast growing and will grow in full sun or semi-shade.
Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.
Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.
van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.