rooftop mushrooms?

Productive rooftops can yield more than just fruits and vegetables.  These cultivated spaces can produce unexpected agricultural products such as wool and honey, but what about mushrooms?  Most fungal species prefer the shade, and yet there are a few species that blossom in full sun.  This morning I launched an experiment to find out if one particular mushroom species has the potential to become a viable, albeit unsuspecting, rooftop crop.

After gathering miscellaneous green roof fabrics, drainage materials, and soil (known as media) from my office’s materials library, I assembled an ad hoc green roof plot on a balcony outside of my office in Philadelphia.  The plot contains approximately 3″ of standard green roof media, and is fully exposed to both sunlight and rain.

New York-based mycologist Sue Van Hook, isolated and cultured a type of edible mushroom called Stropharia rugoso-annulata, and provided me with a bag of spawn with which to inoculate the plot.  Generally speaking, spawn is any substrate that contains mycelium, or thread-like “root” cells.  The particular spawn that Van Hook provided contained a substrate of wood chips and compost.  If the growing conditions are right, this spawn will spread throughout the green roof media and eventually fruit to produce an edible crop of mushrooms.

I spread the spawn on top of the green roof media at a thickness of approximately 1″.  There was no need to water, since the air was thick and the forecast called for rain.  According to mycology guru Paul Stamets, S. rugoso-annulata often takes 12 weeks to fruit, or produce mushroom bodies.  Since my test plot was inoculated in October, fruiting will not occur until next year, if at all.  If the crop is successful, then the potential exists to try it on a larger rooftop scale.  This experiment could very easily fail, or it could be the start of something big.