General Info – summary

This stout and spiny Tree trunk is up to 10m high and 40cm wide.  Bark contains resin ducts.  Olive green Leaves are imparipinnate.  Spaced leaflets have serrated margins.  Flowers are small, dioecious regular & yellowish.   4-merous male Flowers have didynamous stamens.  Female flowers have 1 pistil & a superior ovary.   The resinous Fruit is a small, fleshy drupe producing 1 seed within a bright red, 4-lobed arillode.

Description

Commiphora ugogensis

Zim Tree No. 419 – not indigenous in South Africa.

Common names: (Eng) River Commiphora, River Corkwood.

Family: Burseraceae (The torchwood family, which includes frankincense from Boswellia sacra, myrrh from Commiphora myrrha both of which have an incense like odour).  Neither Boswellia species nor Commiphora myrrha are indigenous in southern Africa.  Non-allergenic resin occurs in most plant tissues.  Worldwide there are about 16 genera and in excess of 500 species, which occur in tropical South America, Malaysia and Africa.  In South Africa Commiphora is the only genus and there are about 20 species that may be regarded as trees.  The Bark is smooth, aromatic and pealing or flaking in small pieces.  The Leaves are resinous and usually without stipules.  The usually dioecious Flowers have 4 or 5 petals and sepals that are imbricate (having regularly arranged, overlapping edges, as roof tiles).  Flowers are actinomorphic (regular, symmetric) and the Stamens are double or equal to the number of petals.  The superior Ovary has 3-5 carpels with 2 ovules in each and the single Style ends in a capitate (forms like a head) or lobed Stigma.  The pitted Fruit is often an edible drupe.

Name derivation:  Commiphora – Greek: kommi – gum and phora – bearer.  ugogensis – of Ugogo in Central Tanzania where the type specimen was found.  Ugogo is situated about 6 degrees south of the Equator.

Conservation Status: unknown.  Consumption of the trees by elephants is a cause for concern in some areas.

Tree

This much-branched Tree is usually up to 10m high and the Stem (main axis of the plant, the leaf and flower bearing as distinguished from the root-bearing axis) is usually fairly straight.  Young branches tend to zigzag and have many spreading angular branches.  As it ages the young green bark becomes rusty red and flaking off in small pieces (photo 922). The up to 40cm wide Trunk is irregular and knobby.  Young grey branches are initially hairy and distinctly zigzag (photo 923).  The outer Bark is initially papery and peals into small flakes.  It becomes pinkish to rusty brown with time.  The pealing reveals a green under-bark (photo 922).  Resin ducts are present in the bark.  Unlike many of our local species, there are impressive stout, single Spines at the ends of small branches (photo 923).  These spines are straight and up to 4cm long.  On this picture are visible Lenticels (a usually raised corky oval or elongated area on the plant that allows the uncontrolled interchange of gases with the environment).  Small hairs cover the young branches.

Leaves

This deciduous tree has olive green Leaves that are alternate or clustered in spur branches.  They are up to 21cm long and imparipinnate (pinnately compound leaf ending in a single leaflet).  Five to 10 pairs of lateral Leaflets are present and paired leaflets increase in size towards the broadly tapering leaf Apex.  Net veining is distinctive.  The single terminal leaflet is up to 7,5 x 2,3cm and is slightly longer than the rest.  Apices are rounded, broadly tapering to slightly acuminate (said of an acute apex whose sides are somewhat concave and taper to a protracted point).  The Base may be slightly asymmetric (not equal to the opposite side) and rounded.  Margins are finely serrated.  Individual hairy on both sides leaflets are ovate to narrowly oblong and have prominent Veins that are much more distinct on the lower surface.  The densely hairy Petiole (leaf stalk) is up to 2,5cm long.  When present, the petiolules (stalks of leaflets) are up to 1mm long.

Flowers

These trees are dioecious (unisexual floral structures with male and female parts on separate plants).  The small yellowish, sessile and bell-shaped Flowers are in axillary sessile clusters on dwarf spur branches.  They appear with or before the new leaves.  The 4-merous (-merous – having a specific number of parts – 4 in this case) flowers are actinomorphic (Regular, symmetrical.  Flowers are vertically divisible into similar halves by more than 1 plane passing through the axis).  The outer pubescent (with dense fine, short, soft hairs – downy) Calyx has very short Sepals (up to 2mm long) that are imbricate (having regularly arranged, overlapping edges) but joined at the base.  The externally densely pubescent and imbricate (having regularly arranged, overlapping edges, like roof tiles) Petals, alternate with sepals and are up to 5mm long.  A cylindrical 4 lobed Disc (a more or less fleshy or elevated development of the receptacle) is present.  The 4 Stamens are didynamous (having 4 stamens disposed in 2 pairs of 2 different lengths).  Two are short (2mm) and 2 are long (4mm) long.  Filaments have attached Anthers in Male Flowers that open through longitudinal slits.  In Female Flowers there is a single Pistil (a unit of the Gynoecium, the female element of the flower, composed of the Ovary, Style and Stigma) containing a 2-locular, superior Ovary.  The single Style ends in a capitate (forms like a head) Stigma.  (Oct-Dec).

Fruit

The small, fleshy Fruit is an almost spherical, slightly flattened Drupe (a fleshy, 1-seeded indehiscent fruit with the seed enclosed in an endocarp – the inner layer of the pericarp or fruit wall.  It is up to 1,8cm in diameter may be membranous e.g. apples or woody e.g. a peach pip stone) which is just under 2cm in diameter.  Fruit is resinous, with a shell-like outer covering.  In southern Africa, the fruit splits into 2 halves when mature, exposing the single bony seed within.  It contains a 4-lobed, bright red Arillode / false aril / pseudo aril (a structure in certain seeds that resembles an aril but develops from the micropyle of the ovule as opposed to the stalk).  This arilode has a wavy margin that covers more than half the single hairless Seed.  The arillode has 2 long, corrugated arms and 2 short, triangular arms.  (Jan-Apr).

Distribution & Ecology

These plants are Located in Northern Zimbabwe along alluvial flat areas, on sand and along rivers including in the Zambezi valley.  Trees also occur in Tanzania, Mozambique (northern – close to the coast) and Zambia.  This tree may form thickets.  It is commonly found in areas with an annual rainfall between 800-1 400mm.

Ethnobotany

Fruit is edible.  Propagation is from seeds or cuttings.  The plant requires full sun and warm temperatures.

References

Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.

Burrows, J.E., Burrows, S.M., Lotter, M.C. & Schmidt, E. 2018. Trees and Shrubs Mozambique.  Publishing Print Matters (Pty) Ltd.  Noordhoek, Cape Town.

Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.

van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.

http://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=133400

https://www.cabdirect.org/cabdirect/abstract/19510600756

http://file.scirp.org/pdf/OJE_2016012714533000.pdf

http://posa.sanbi.org/flora/browse.php?src=SP

http://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:127848-1

http://www.theplantlist.org/tpl1.1/record/kew-2733721#:~:text=Commiphora.%20Commiphora%20ugogensis%20Engl.%20Commiphora%20ugogensis%20Engl.%20is,publication%20details%3A%20Bot.%20Jahrb.%20Syst.%2034%3A%20314%201904.