'Crataegus monogyna' and 'Prunus mahaleb' are two related fleshy fruiting shrubs that were introduced to Australia as ornamental and commercial plants in the nineteenth and twentieth centuries. 'C. monogyna' is very invasive in the region, having spread rapidly and conspicuously throughout northern New South Wales and elsewhere in south eastern Australia. 'P.mahaleb' is far less invasive, being restricted to a small and slowly expanding population near Armidale in northern New South Wales. Calculation of rates of spread of both species by analysis of annual growth rings indicated that 'C. monogyna' is spreading at 80 m yr ⁻¹ , four times faster than 'P. mahaleb' which is spreading at 20 m yr⁻¹
