Buoyancy of Florestina tripteris seed, an invasive exotic weed of Central Western Queensland

Abstract

Sticky florestina (Florestina tripteris DC.) (florestina) is an invasive weed present in central western Queensland. Recent higher rainfall years have aided the spread of florestina and there is potential for further increase in abundance and distribution. Florestina has several vectors for spread including vehicles, machinery, animals and waterways. Currently, the potential dispersal distance of florestina seed along waterways is unknown. This study investigated the duration of florestina seed buoyancy to determine potential dispersal distances in flowing water.

The buoyancy of florestina seeds was tested in a laboratory by placing lots of 50 seeds in 800 mL beakers containing 350 mL of water and subjecting them to various levels of agitation (no, low and high agitation). The length of time seeds remained buoyant was recorded. After an hour, 55.6% of seed remained floating in the no agitation treatment compared to 34% and 18% in the low and high agitation treatments respectively. After seven hours, 10% of seed remained floating in the no agitation, 11.6% in the low agitation and 5.6% in the high agitation. Greater than 94% of seed for all treatments had lost buoyancy within 24 hours of being placed in the water. The remaining seed stayed floating for various lengths of time with one seed still floating after eight days in the no agitation treatment. By having a greater understanding of how florestina spreads across the landscape, more effective management plans can be developed to improve land management outcomes.