Effects of garden type and distance from bush on adventive trees in domestic gardens

Gardens are both a source of plant species that invade native vegetation (bush) and are places that native species can invade. We test the hypotheses that the richness of adventive exotic and native trees in suburban gardens declines with distance from the bush, and that the type of garden strongly influences the establishment of adventive trees. The adventive woody species in front gardens of houses on randomly selected streets in three Hobart suburbs were observed from the street, along with garden type. Distance from the bush boundary was measured from maps. Most taxa occurred less frequently with increasing distance from the bush and garden type was associated with the occurrence of several taxa. Distance and garden type had no effect on the exotic Pittosporum undulatum, possibly because it is rare in native vegetation due to its fire sensitivity but is both attractive to many gardeners and well-dispersed by birds between gardens.