Across much of southern Australia, especially in the south-eastern states, African Boxthorn (Lycium ferocissimum) causes great angst for both farmer and conservation manager alike. Aptly named, this woody weed is indeed ‘ferocious’, often forming impenetrable spiny thickets that can invade remnant bushland, providing ideal protection for feral cats, foxes and rabbits, and even hosting pest insects including fruit fly. African Boxthorn was first introduced into Australia from the Cape Province of South Africa in the mid-1800s for growing hedgerows, but it has progressively spread across the landscape, infesting degraded and unmanaged ground. Its threat to the environment has been recognised and is declared as a Weed of National Significance (WONS) and a noxious weed in the south-eastern states of Australia.
African Boxthorn is a member of the tomato family (Solanaceae) and can reach up to 5 metres in height, with the many-branched thorny stems reaching the ground and providing harbour for rabbits and foxes. The leaves are oval-shaped, bright green and clustered along stems; flowers are white to purple with 5 petals; the ripe fruit an orange-red berry (poisonous to humans). Plants are more commonly found on well-drained soils, but extend in range from the cool winter climate of Tasmania through to the warm sub-tropics of Queensland.
It is very common to see the removal of African Boxthorn listed as a priority action in a Conservation Management Plan, particularly where rabbits and foxes are also being controlled. In the more degraded landscapes, there are cases where retention of African Boxthorn is justified, at least until suitable replacement shrubs become established, including Sweet Bursaria, Hakea and prickly Acacia species. Arguments to temporarily retain African Boxthorn may include the protection they afford to nesting and roosting birds, particularly rare finches, small parrots, and thornbills. In all instances, African Boxthorn spread should be controlled, with a plan for ultimate removal and replacement with native species.
The typical management method of dealing with African Boxthorn is manual removal, either by uprooting with an excavator (in areas of dense infestation of mature plants), or by cutting the stem and treating with herbicide. Cut plants should be piled and burnt, as dead material is remarkably robust and tolerant to decay and will continue to provide harbour for feral animals. Re-emerging seedlings at an infected site can be hand-pulled or sensitively treated with an appropriate woody herbicide.
African Boxthorn is being actively removed and controlled on the Wilderlands projects, Coorong Lakes and Budgerum Grasslands. On these reserves, long-term eradication is the goal.
Did you know that Australia also has a native boxthorn? Yes, the Australian Boxthorn (Lycium australe), preferring a drier climate and often fringing saline lakes or in sub-saline soils. It is important for our conservation managers to recognise the differences of these two species, to ensure our native boxthorn is not accidentally removed.
Chris Lindorff, Wilderlands Chief Ecologist, is an experienced ecologist and land manager with a degree in Science, and Forest Science, from University of Melbourne.