Bursaria spinosa is known as the Blackthorn and also the Tasmanian and South Australian Christmas Bush because summer is the principal flowering period. Blackthorn develops into a medium to tall shrub with oval leaves, shiny on top and dull underneath. The branches also carry large spines. In summer the plants are smothered with masses of creamy-white fragrant flowers. Bronzy capsules follow the flowers. Bursaria spinosa is one of the shrubs, which has regenerated vigorously at Yallaroo since sheep and cattle were removed.
B. spinosa 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.). These insects parasitise Scarab beetle larvae. Scarab Beetles defoliate eucalypts and are one factor in the demise of these trees in the Northern Tablelands. The wasps use Blackthorn flowers as a food source.B. 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.