Conservation introduction of the parasitic plant dactylanthus at Waipapa, New Zealand

Summary

Dactylanthus (Dactylanthus taylorii), New Zealand's only fully parasitic native flowering plant and now nationally vulnerable after introduced browsers like possums and rats suppressed its fruit production across roughly 85 remaining populations, was the subject of the first fully monitored experimental establishment trial, run by the Department of Conservation at Waipapa in the central North Island starting in 1999. Researchers set up 24 permanently marked seeding plots across four sites with suitable host trees but no existing dactylanthus, each sown with about 1,500 seeds either spread across the plot or concentrated in a small central grid, and covered with mesh cages to exclude pollinators and rodents so establishment could be attributed solely to the initial sowing. Establishment was first confirmed four years after sowing at two sites; by ten years, dactylanthus had established at all four sites and in 22 of the 24 plots, with inflorescence numbers per plot matching or exceeding those in wild populations. Centrally sown plots established plants sooner, while broadly sown plots ultimately produced more inflorescences due to less crowding; unexpectedly, trial plots showed a strong female-inflorescence bias, up to 100%, opposite the roughly 5:1 male bias typical in the wild, though the male share rose over the final years. The one open-canopy site showed delayed, weaker establishment, possibly from drier soil or an unoptimized early sowing technique. Major difficulties included variable annual flowering timing and a four-fold rise in monitoring workload as inflorescence numbers grew. The project rates itself Successful, though results have not yet been replicated at other sites using the same methods.