Open Access

Petrus C. Heyligers

• Gladiolus gueinzii (Iridaceae) and Trachyandra divaricata (Liliaceae s.l.) are South African dune plants naturalised in Australia. Gladiolus gueinzii has two modes of dispersal: winged seeds, and cormels that may float for up to seven months in seawater. Its Australian occurrences are restricted to New South Wales. It was first collected in 1950 near Newcastle and has spread 250 km to the north and 500 km to the south. From large distances between the early herbarium records it was inferred that buoyancy of the cormels enables Gladiolus gueinzii to establish at sites remote from existing populations. The climatic conditions of the area over which Gladiolus gueinzii presently occurs are broadly similar to those of the more humid part of its native range. Further spread may be restricted due to unfavourable thermal factors. Trachyandra divaricata is a "tumbleweed". Wind dislodges and carries away the "crowns" of tangled mature infructescences, in the process peppering their trails with innumerable small seeds. In the 1930s Trachyandra divaricata became established near Perth, Western Australia, while in 1940 it was also found near Karridale, 300 km further south. In the intervening area it has become a major weed in the dunes and has spread to paddocks inland, causing poisoning of livestock. Trachyandra divaricata has also turned up at several other outlying coastal locations as well as at an inland site. The distances involved are suggestive of dispersal by human agency, for instance through cars or boats. The Mediterranean and adjacent semi-arid climates of the south-west of Western Australia mirror a similar situation in southern Africa. Hence, the area appears to be well suited to Trachyandra divaricata and further spread can be expected. In New South Wales Trachyandra divaricata was first found in 1968 at a dune rehabilitation site near Wollongong. It possibly came in as a contaminant of Acacia saligna planting stock from Western Australia. Since then it has become established at several other reclaimed areas, but has not spread much beyond such sites, possibly because of unfavourable climatic conditions. Nevertheless, in case aggressiveness takes a turn for the worse, it would appear desirable to eradicate occurrences in New South Wales while this is still achievable.