Bursaria spinosa, Blackthorn
Bursaria spinosa is known as the Blackthorn and also the Tasmanian and South Australian Christmas Bush because summer is the main flowering period of this prickly plant.
Blackthorn develops into a medium to tall shrub with oval leaves, shiny on top and dull underneath. The branches carry large spines. In summer the plants are smothered with creamy-white fragrant flowers. Bronze capsules follow the flowers.
Bursaria spinosa is one of the shrubs which have regenerated vigorously in our cold climate garden since sheep and cattle were removed two decades ago.
Blackthorn is an environmentally important native plant. The prickly branches provide secure nesting sites for small native birds. In our clumps of Blackthorn there are many nests visible from previous year’s breeding activities. The flowers are a source of nectar and attract a range of insects including handsome Blue Flower Wasps (Scolia sp). Female wasps paralyse and lay eggs on the Scarab or Christmas Beetle larvae. Scarab Beetles defoliate eucalypts and are one factor in the demise of eucalypts on the Northern Tablelands of New South Wales.
Bursaria spinosa is also important in the survival of the Bathurst Copper Butterfly (Paralucia spinifera). Bathurst is an inland city west of Sydney, across the Blue Mountains. In this area, Blackthorn is the principal food plant of this rare butterfly that has limited range and distribution. A planting and weed control programme is underway to ensure the survival of the Copper Butterfly.
The photo shows a Spotted Flower Chafer Beetle (see article) burrowing into the flowers seeking nectar.
Propagate Blackthorn from seed or cuttings.
Warren and Gloria Sheather