Cordeauxia

C. edulis is a drought resistant plant and tolerant to desertification. For optimal plant development, average temperature and rainfall requirements are 25 °C and 250 - 400mm/year (two rainy seasons).[8] Occasionally the Yeheb tree can also cope with minimal precipitation levels of 150–200 mm/year. It grows on red sandy soils (called Haud) with a low nitrogen content. The soils are alkaline and their texture is fine to coarse sand or grit to loamy sand.[5][9][15] C. edulis prefers elevated stands, where no water accumulates. It grows in altitudes between 100–1000 m and is found in vegetation with acacia-commiphora deciduous bushland and thickets.[12]

The seed is often said to be viable for a few months only, but seed coated in wood ash and stored in a sack is reputed to remain viable for at least a year. The seeds should be sown on soils where the taproot can develop. There is no information available on optimal density and spacing. Under natural conditions there are up to 320plants/ha. The seedlings need ample water after planting. A transplantation of the plant destroys the taproot and leads to mortality.[4] C. edulis grows slowly in the early stages, because of the buildup of the strong taproot and the small proportion in reserve proteins.[5] Once the plants are established, they need almost no care.[4] The plant is self-reseeding, but due to the fact that seeds are often infested by weevils and larvae or roasted in the post-harvest treatment, it is difficult to obtain viable seeds for planting. The plantation established near Voi, Kenya, is currently the sole source of germplasm.[14]

The yeheb seeds are usually harvested from wild plants.[4] The recommended harvest time is in June,[16] but in Somalia nowadays the harvest is reported to occur twice a year.[17] This is possible if both rainy seasons occur within their normal extent and contribute enough rain for the plant. The Yeheb-Nut is mainly harvested manually by children and women,[17] and the harvest process is described as hard work. Due to the high demand and many droughts in the last few years, the shrub is often harvested immature at an age below 3 years.[14] The plants are often overused as the people remove all seeds at the same time.[4]

Yeheb produces few fruits in the first three years, but it can live up to many years. The quantity of the yield increases with higher age, but also depends on the amount of rainfall. The yield is about 5–8 kg seeds.[18] The estimated average forage production is 325–450 kg/ha.[4]

The seeds are rarely eaten fresh by Somali children, more often they are first dried in the shade during 7–10 days and then the hard seed coat is removed. For storage, the seeds have to be roasted or boiled to prevent fungal attack, to kill insects eggs and larvae inside the seeds and to harden the seed coat.[4] After roasting in the hot ash, which leads to yield losses due to damage of the seeds, the seeds are coated in weed ash and stored in sacks in the house for personal use or for trade at local markets at a later time.[17] The seeds treated this way are storable for about one year.[9] Pastoralists keep the seeds in containers out of dried and tanned camel leather, where they can be stored for many years.[4] The firewood for roasting is often taken from the shrub, which hampers the regeneration of the population in addition to the complete removal of all the seeds.[9]

• Food: The seeds are eaten dried, boiled, roasted or raw.[5][15] Sometimes the seeds of C. edulis is the only available food for Somali nomads during droughts. The seeds are nutritious and taste sweet with a chestnut flavour after roasting.[1][4] Fresh or dried seeds taste sour. Local people like its taste so there is a saying Fadhi iyo Fuud Yicibeed lays la waa”, which means: Those who remain seated and laze will not get Yihib.[6] The raw seeds contain a considerable amount of serine protease (trypsin) inhibitors, causing nausea or stomach distress. These inhibitors are destroyed by heating during cooking or roasting.[8]
• Drinks: People made a tea out of the leaves[5][15] or drink the sweet water in which the seeds have been boiled as a beverage.[1][4]
• Medicine: C. edulis can regulate gastric secretion. A study showed that the consumption of the plant enhances the production of erythrocytes and is therefore used as a remedy for anemia.[4]

C. edulis is an important bee forage.[7] Furthermore, it serves as fodder for camels, goats, sheep and cattle in dry season[4][19] but the shrubs cannot withstand long-term grazing pressure.[5][15] It is essential for the livestock production, especially in central Somalia and eastern Ethiopia where C. edulis can cover 85% of the good-quality feed during the dry season.[20] During the rainy season, the animals usually avoid the plant because of its high content of tannins in the leaves (see table below).[5][15] The leaf content of K, Ca, Mg, S, Ni, Cr, V and Ti is adequate. The content of N and P is low, whereas the latter is probably a consequence of the low P stock in the soil. Al and Fe content is high, probably due to dust. Also, the Ca/Mg and Ca/P ratio is too high. Overall, there could be problems to cover the demand of P, Mg, Mn and partly Zn of grazing stock by feeding only Yeheb.[21] C. edulis can cause intestinal disorders in goats when eaten as the sole diet.[4]

C. edulis also contains a naphthoquinone, cordeauxione (cordeauxiaquinone). It is found in the glands of the leaves and is unique for C.edulis. It is used as a red dye. If goats browse on the leaves of C. edulis, their feet become light-orange in color and their urine turn purple.[6][20] As Cordeauxione makes calcium complexes, teeth of animals get orange-red and their bones pink when they eat the leaves.[4] The pink bones are considered a sign of good meat quality in Somalia and Saudi Arabia.[4]

• Fuel: The wood is a good firewood, also when wet.[4][5][15]
• Insect defence: Roasting or boiling of freshly picked seeds provide a good insect defence.
• Industry: The red dye in the glands of the leaves can be used for dyeing textiles.[5][15] The dye can also be extracted by alkaline or acid dissolver, whereas first leads to a more intense violet color.[4]
• Soap: Soap can be made out of the seed oil.[4]
• Construction timber: The wood is popular as a building material due to its resistance to termites.[17]

• Livestock fences[7]
• Nitrogen fixation[7]
• Soil conservation[7]
• Mulch[7]