Invasive alien plants of horticultural origin growing in Zimbabwe: Analysis of control mechanisms and management.

Abstract

Alien ornamental plants which escape from cultivation usually establish themselves and invade other habitats with far-reaching ecological and economic consequences. The current study, conducted in Zimbabwe, assessed the diversity of invasive alien ornamental plants in the country, the life forms of the species, their continents of origin, preferred invasion habitats, management and spread of the species. This study therefore focused on alien ornamental plant species which reproduce or spread without continued human help. An extensive literature review resulted in the identification of 41 invasive alien plant species used as ornamentals in Zimbabwe. Documented species belong to gymnosperms (4.9%), ferns (7.3%), monocots (9.8%) and eudicots (78%). More than half of the ornamental species (65.9%) are members of the Solanaceae family with six species, followed by Asteraceae and Fabaceae (five species each), Euphorbiaceae (three species), Cactaceae, Meliaceae, Pinaceae and Salvinaceae (two species each). About three-quarters of invasive alien species used as ornamentals in Zimbabwe (70.7%) are native to America, followed by Asia contributing six species (14.6%), Africa and Oceania with four species each (9.8%). Results of this study showed that degraded areas, roadsides, riparian habitats, woodland and forest formations are the preferred invasion habitats of invasive alien species used as ornamentals in Zimbabwe. Results of this study are important for monitoring existing alien plant species in the country, new introductions, and managing biological invasions. A better understanding of their establishment, spread, social and economic impacts, and distributional changes over time is vital for making informed decisions about alien plant species.