For the first time we have to consider what to do when we actively introduce a native species to the garden unintentionally.
In this case I was recently visiting a private woodland (with the owners permission) and I came back with a small branch I felt would look nice alongside the wetland/pond area we created. I should add that the woodland, suffering from ash dieback, was not lacking in dead, dying or decaying wood, either standing or fallen.
Anyway whilst placing the branch I noticed the presence of Green Elf Cup, an amazing looking species not seen in the garden before.
Our thinking on this is the same as the wildflower species we are attempting to introduce. We will record it as present in the garden. If it establishes itself (we record it next year onwards) then great, we have a new species. Ultimately any material brought into the garden could in theory be harbouring a stowaway species.
Hopefully it will be able to adapt to conditions outside of the woodland. I may now place it beneath the shrub line, but I gather it is frequently recorded in gardens. Indeed it is a widespread species. There is a similar species it could be but this is much rarer, Chlorociboria aeruginosa. For now we will assume we have this one correct as the Green Elf Cup and welcome to the garden!