- History and Culture
Ligustrum robustum is a shrub measuring up to 5 meters high, native to South and Southeast Asia. The shrub was introduced to Mauritius and Rodrigues and subsequently to Reunion and is currently considered a major invasive species. The shrub has white speckled twigs and arched stems on which terminal panicles of small white flowers grow. The tree produces bluish-purple drupes or fruit which are fleshy and contain one seed.
In its native range, the shrub occurs up to 1500 meters in wet and intermediate low montane regions in Indian and sub montane forests in Sri Lanka. It is known to grow near streams. In the Mascarenes it is common in lowland forests. L. robustum was introduced into Mauritius as an ornamental plant and as a hedge plant in Rodrigues and Reunion. The plant is self-pollinating and produces fruit over six months of the year. Birds who ingest the fruit contribute to dispersing the seeds over long distances through their droppings.
L. robustum is considered an invasive species. There are several factors that contribute to this status: it has dense foliage, which reduces the light reaching the forest floor preventing the regeneration of plants; it competes with other plants for space and affect nutrient and water cycling, altering the structure and composition of the forest, and finally the species competes with other native species for space and nutrients, thereby displacing them and altering successional patterns. In addition, its rapid growth rate, ability to tolerate high shade conditions and high seedling recruitment further contribute to its invasiveness.
Introduced as an ornamental plant, L. robustum was further propagated and planted in Mauritius to protect conifer plantations from deer, and ironically, to help control other invasive weeds.