spores growing and developing, but once the amount has gotten to a mass level, it becomes visible to the naked eye. This can be problematic because you could have been smoking this contaminated weed and not even have known it. Usually, a good way to judge is by using your other senses....
First, several people mentioned that they use weed barrier fabric in their vegetable gardens and at the end of each growing season they pull it up and re-use it again the following season. I think one even mentioned washing it. For this purpose, I think the weed barrier fabric would be ...