Species characteristics Life form, size, lifespan Thorny small tree growing to a height of 7 m. Lives at least 60 years. Taxonomy, variation and plasticity Nine sub-species are recognised. Hybridization between the various ssp. Within the A. nilotica complex the pods are very variable. The yellow sweetly scented flowers are nectarless and found in round heads.
Most flowers are functionally male with a few hermaphrodites and are mainly bee-pollinated.
Pods are indehiscent. In Kenya seed set per pod was 10.8 and trees produced between 153 and 34,000 seeds. Leaf production and fall are affected by rainfall whereas temperature affect flowering and fruiting. May. In Australia trees flower from March to June and green pods are produced within four months but ripe pods fall from November to February. Most of the leaf fall occurs during the dry period when the tree bears green pods.