This taxon is extremely variable and widely naturalised.The name r. fruticosus sp. agg. is applied as an aggregate name to all the species of subgenus Rubus, including r. ulmifolius Schott, Bramble, (and its hybrids) and several other species.
R. fruticosus is a widespread noxious weed in SE Australia and in SWWA, purportedly originally spread as seed by early explorers trying to ensure a food supply for themselves and others on future expeditions. It was also used to control soil erosion and as a hedging plant. Now the blackberry is unquestionably one of the most devastating weeds in Australia, costing tens of millions of dollars in reduced production and costs for control, as it spreads rapidly and competes successfully with other vegetation. Biological control using rust fungi has been investigated and in 1984 a rust was released illegally, first in S Vic; it has now also been released in other states. In 1991 further strains were officially released to act as growth-suppression agents.Of the various 'micro'-species about 75% are susceptible. Once infected, these lose about 10% of their biomass per year. However, susceptible plants are being replaced with unsusceptible ones, so progress is difficult to assess and research continues (Mr Eligio Bruzzese, pers. comm.).
The cultivar 'Silvan Blackberry' was developed in Australia by Agriculture Victoria in the 1960s and is more popular than the Boysenberry and Youngberry among both commercial growers and home gardeners. It is an extremely hardy cultivar producing fruit in Dec.
Recent research indicates that there are about 40 'micro'-species naturalised in Australia.
Source: (2002). Rosaceae. In: . Horticultural Flora of South-eastern Australia. Volume 3. Flowering plants. Dicotyledons. Part 2. The identification of garden and cultivated plants. University of New South Wales Press.