I am not sure how it works but think that there are areas which have more parasitic plant. In my regular area I get 3 to 6 plants while filling up my 2 packies with wood and mostly bark and other areas maybe 1 or 2. I seem to get the luminescent fungi to make the other poison much more frequently. I have yet to seriously experiment with either of those earthen mixture poisons. I have been chopping wood to gm my carpenter (just gmed). Now I am going to have to do it to get parasitic plants.