So how were we going to tell if the imported Topsoil had such propagules? We had to adapt. We knew that labs were available that could tentatively identify roots, if picked up in foundation exposures. Therefore it followed that they should be able to identify them in Topsoil samples. So, Topsoil samples were sieved, and potential propagules picked out and sent off for laboratory analysis.
Although analysis is tentative when root/propagule sections are thin, it was possible to cross-reference the species of the roots identified in soil samples where invasive weeds had grown and had not grown.