First records of Amaranthus palmeri, a new emerging weed in southern Africa with further notes on other poorly known alien amaranths in the continent

Abstract

Amaranthus palmeri is native to Mexico and the south-eastern parts of the USA, and is reported as alien in subtropical regions of the Old World. Previous records from Africa were from the northern parts of the continent. This species was first found in South Africa in March 2018 with further records in different regions of the country as well as in northern Botswana in March 2020. We consider it as naturalized weed which invades both ruderal and segetal plant communities. Mechanical control of A. palmeri plants may be effective to minimize its spreading, because at the flowering stage these tend to be taller compared to other amaranths. Those species of the genus alien in Africa are discussed in terms of their distribution and possible invasive status, particularly A. dubius and A. standleyanus.