These are thought to be hybrids between the Hybrid China Tea roses and, probably, R. pendulina, R. majalis, R. blanda or related species. R. blanda has been used to breed thornless roses. The main features of the group are the arching habit, the early, slightly fragrant flowers, and stems with distinctive deep red bark that is devoid of prickles.
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.