Watsonia Watsonia is a garden escapee that belongs to the iris family. It spreads by corms and cormils and competes with native vegetation. Hawthorn Hawthorns are perennial erect deciduous shrubs or small trees. The stems have many stout branchlets terminating in spines. The white, cream or pink flowers give rise to red berries about 1 cm in diameter.
Hawthorns invade disturbed bushland and form spiny thickets.
They provide cover for rabbits and other pests, and are an alternative host for the fireblight bacterium that attacks apples and pears. Olives that are not planted and maintained for domestic or commercial use are proclaimed as pest plants for most of the Mount Lofty Ranges. This sometimes causes confusion for landholders who are contemplating the deliberate planting of olive trees. Current wild olive infestations have mostly arisen from deliberately planted trees. Seeds are spread by birds and foxes.