Early detection ofemerging invasive plants depends onmaximizing the probability of detecting newpopulations.
Repeated surveys along a gradient of environmental conditions or in areas exposed to high propagule pressure
provide a potentially efficient strategy for early detection of alien species. The long-term monitoring of such an
area resulted in the documentation of the first naturalised Solidago gigantea Aiton (Asteraceae) population for
southern Africa. This population consisted of c. 45 individuals growing in two locations on unmanaged grassland
in the Drakensberg Mountains at an elevation of 1619 m a.s.l. Solidago gigantea readily invades unmanaged
European grasslands, altering biomass and transforming habitats. Moreover, since goldenrods (Solidago spp)
are perennial species reproducing through a large number of wind-dispersed seeds and belowground rootstocks,
these species appear well pre-adapted to the fire-prone grassland biome of South Africa. We therefore suggest
early-stage eradication of S. gigantea before it potentially becomes an unmanageable and costly invasive species
in this region. This study supports long-termmonitoring programmes as an effective means for early detection of
new invasive species.