The genus Ximenia includes eight species. It belongs to the botanical family Olacaceae, which has a pantropical distribution and is found on most continents across the world, in Africa, the Americas and Australasia. The genus was named in honour of a Spanish monk, Francisco Ximenez, who wrote about the plants of Mexico in the 17th Century. Ximenias are drought-resistant, spiny shrubs. Their fruiting is largely dependent on rainfall and other weather conditions. In Namibia, botanists recognise two species, one with a single variety and the other with two varieties:
- Ximenia americana var. americana, the species that is currently commercialised. It is most abundant in the current TTC area (Ohangwena and Oshikoto regions).
- Ximenia caffra var. caffra, the fruit of which is commonly eaten. The oil of this species could prove to be commercially interesting as well, but it is different to the oil of X. americana.
- Ximenia caffra var. natalensis, which is the least abundant subspecies in Namibia and is only rarely found in the far north-east of the country.
However, previously, an additional variety of X. americana – var. microphylla – was also thought to occur in Namibia. In fact, it was regarded as the more common of the two varieties. This project found that there did appear to be two distinct forms of the species, based on their different general appearance, fruit size and seed oil composition. In the dry Kunene Region, ximenia shrubs are mostly found along watercourses, but in drought years barely any fruits can be found. The large sour plum (X. caffra var. caffra) is commonly eaten, while X. americana is reserved for making the traditional oil used as a skin ointment. The variety occurring there was identified as X. americana microphylla, which presented an oil composition slightly different from the variety americana, the specifications of which is presently used in the international cosmetic trade. Kunene inhabitants to some extent harvest ximenia for their own use, but the resource is not very abundant. It is discussed below, but note that it could prove to be just a geographic variation of var. americana rather than a distinct variety.
- Ximenia americana var. microphylla, also used traditionally for making oil, but the oil composition is slightly different from the variety that is currently commercialised. This variety is more dominant in the north-eastern and north-western regions of Namibia.
Although ximenia shrubs/trees are found in a wide area in the northern half of Namibia, from the Kunene Region to the Zambezi Region (formerly Caprivi) and down to parts of the Otjozondjupa Region, their abundance, species and varietal distribution varies between regions and locations.
In the Kavango and West Zambezi Regions, the ximenia shrubs are not associated with a particular vegetation type and occur sporadically throughout the various woodlands and shrublands. X. americana var. microphylla is generally more abundant than the other americana variety and X. caffra appears far less abundant.
Although the density of shrubs per hectare in some conservancy and community Forest areas was found to be similar to the prime harvesting area of TTC in the Ohangwena Region, it was observed that the fruiting productivity of the shrubs was very poor.
This was partly the result of frosts, to which ximenia shrubs are sensitive, but also because of the direct impact of veld fires that are recurrent and widespread in these Regions. With the poor quality of shrubs in these Regions, commercial harvesting for community income generation does not seem a viable option at present.
In the North-central Regions where ximenia is generically known as Eemheke or Eembeke, the abundance of ximenia shrubs varies greatly. The thorny tree is mostly found on communal land in areas that are less populated. In the more densely human populated areas, the ximenia resource has greatly reduced over the years, most probably due to the clearing of land, deforestation and grazing by domestic animals.
In some places ximenia has almost completely disappeared. This greatly contrasts with the TTC harvesting area in the Ohangwena and Oshikoto regions where ximenia is abundant, particularly in an area stretching from around Ondobe-Eenhana down to Ohepi and Omuthiya-Omuntele. It is in these areas that the variety X. americana americana is by far the dominant variety compared to the other ximenia subspecies. Surprisingly, ximenia is rarely found further east towards Okongo.
Although the distribution pattern of ximenia is patchy, high densities of shrubs above 40 per ha (up to 140 per ha) have been counted in localised pockets that form the main harvesting areas, varying from less than 2 km to 7 km in diameter. Harvesters’ estimates of the age of some of the larger trees ranged between 40 and 70 years, and young trees start producing a substantial fruit harvest after 4–10 years. Large numbers of seedlings and small plants of ximenia species have been observed, indicating that recruitment is taking place in the harvesting areas, although the seedlings are often eaten by goats.
However, ximenia shrubs are still felled for building poles, brush wood fencing, and clearing land, which represents a threat to the resource. This could potentially be counterbalanced by the new value given to the shrubs/trees by the commercialisation of ximenia products.
In the longer term, propagation of ximenia trees has the potential to increase harvesting volumes and reduce the present harvesting effort of collecting ximenia fruits from distant trees that need to be visited regularly throughout the fruiting season. Propagation also seems a necessity to counteract bad harvesting years, which make supply unreliable and are thus currently a threat to commercialisation of the resource.