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Blackthorn develops into a medium to tall shrub, up to potentially 10 metres tall but usually smaller. It tends to always have a shrub-like habit rather than a true tree, spreading to a few metres wide potentially.
It has a large natural geographic range, up and down the NSW coast, tablelands and western slopes and out into the western plains (as far west as around Griffith-longitude). It extends right up the Queensland coast as well as through most of Victoria and Tasmania, extending as far as Streaky Bay and further north of, in South Australia.
It can be found in wet to dry sclerophyll woodlands and forests and sometimes forming its own shrublands. It can form dense thickets in regenerating areas and as a midstorey species. It can be found on a range of soil types from heavy clays to alluvium, rocky outcrops and sandstone-based soils.
Bursaria spp. have simple and alternate-clustered leaves. In this species, leaves are mostly dark green (when mature), shiny on top and dull underneath, narrowly-elliptic to linear-obovate to narrow-ovate, to 45 mm long and to 12 mm (usually much narrower) wide and heavily clustered on branches. The branches carry large spines.
Bursaria spp/ produce 5-petaled, white bisexual flowers, with 5 stamens and 1 carpel. In summer, this species is laden with creamy-white stellate and fragrant flowers, each flower up to 10 mm across, produced in pyramid-shaped terminal panicles to about 25 cm long by 10 cm wide, which can create a showy display.
Distinctive bronze, flattened heart-shaped capsules follow the flowers, up to 1 cm long and wide.
An easy and useful plant to grow in a garden. It may not be preferred due to its thorny nature and possible difficulty in undertaking maintenance. However, it could be grown in out-of-the-way areas and also used as a barrier planting. Very hardy once established. If any gardener wants to attract small native birds into their patch, then this species is likely in the top-10 that should be considered. This Editor has done just that on a not often-accessed cliff-road-verge, so that the small birds might come in.
Blackthorn is an environmentally important native plant. The prickly branches provide secure nesting sites for small native birds.
Authors note: 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. 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.
It can self seed in the right conditions. Can be pruned to create dense shrubs and to keep at a lower height.
The thorns easily embed themselves in the skin. Areas of skin affected quickly become swollen and irritated so remove thorns as soon as possible. Handling prunings can be difficult. It is likely best to rake them up and leave them in a pile.
Plants can be affected by sooty mould and scale in some cases.
The photo shows a Spotted Flower Chafer Beetle burrowing into the flowers seeking nectar.
Plant in full sun for best results with some room to spread but keep away from traffic-areas. It is often found naturally on clay to alluvial soils but can be found on sandstone as well – so will likely thirve in most gardens. Very hardy once established.
Propagate Blackthorn from seed or cuttings.
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.
Two subspecies are currently recognised in NSW,
This species regenerates easily after fire from suckering and coppicing of burnt plants. It also regenerates from the seed bank.
Terry Spencer, a resident of Jerrabomberra (a suburb of Queanbeyan), brought our attention to an article in the Canberra Times (4/11/22) which describes new populations of Paralucia spinifera in Namadgi National Park in the ACT. https://www.canberratimes.com.au/story/7968493/recently-discovered-rare-purple-butterfly-thrives-in-namadgi/
Wonderful news that this beautiful (but dainty) butterfly is located beyond Bathurst.
Bursaria is a small genus of 6 species, endemic to Australia, occurring in all states except the Northern Territory. NSW currenty has 5 species.
Bursaria – Latin from Bursa meaning “purse” – referring to the purse-like appearance of the capsules.
spinosa – Latin meaning “prickly” – referrring to the sharp spines on the branches.
This species is not considered to be at risk of extinction in the wild.
NSW Flora Online (PlantNET) – Bursaria spinosa profile page https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Bursaria~spinosa
Wrigley, J.W. & Fagg, M.I. (2001). Australian Native Plants – Propagation, cultivation and use in landscaping. 4th edition. New Holland Publishers, Pty. Ltd. Australia.
Gardening with Angus – Bursaria spinosa profile page https://www.gardeningwithangus.com.au/bursaria-spinosa-sweet-bursaria/