Gourmet Mushrooms

About Mushrooms

To be honest, mushrooms are strange organisms. They can be microscopic, or the single largest organism (by area) on this planet. Furthermore, there's been proof that they allow for inter-species communication between various flora in their environment, giving some trees the ability to produce extra antibodies or toxins if viruses or pests have been chewing on their neighbors. But they're also thought of as annoyances when they cause your Athlete's Foot or devour stands of trees. So, what exactly are they?

What Are Mushrooms?

Mushrooms are probably the most recognizable classification of fungus. These bulbous, fleshy things are only the sprouting fruit of a vast underground network that can intertwine with other species' root systems, acting as an inter-species highway. They're typically found above the soil or covering the surface of whatever food source they're recently colonized.

Interestingly enough, while most of us could see something and say "that's a mushroom", there's no agreed upon scientific basis for what exactly a mushroom is. The individual species can vary so much from one-another that over 14,000 different organisms are called "Mushrooms".

Unlike plants, Mushrooms produce spores — microscopic, seed-like particles that are essentially clones of the mother plant. Mushrooms can also reproduce sexually by sending out long fibers. Once these fibers discover the fiber of another mushroom, they exchange DNA, produce a mushroom of their own, and send out spores.


Fungi are thought to have diverged from other lifeforms up to 1.5 billion years ago, meaning that they are as distantly related to bacteria as they are to us. However, the oldest preserved example of a Mushroom is from approximately 400 million years ago as they don't mineralize well. Due to the non-consensus of what exactly Mushrooms are, however, nobody is quite sure if the fossil is actually of a Mushroom or of a stem fungus. Many scientists argue that the first mushrooms probably existed between 90 and 94 million years ago due to the humid environments of that era and evidence of spores in amber.

Amanita muscaria, a type of toxic mushroom. Image borrowed from Wikipedia Commons

Edible Mushrooms

Mushrooms have commonly been used in Asian and European cuisines for thousands of years despite being neither meat nor fruit nor vegetable. Mushrooms are a vegan food are are often substituted for meat in recipes because of their texture and taste. They also contain a significant amount of protein which is highly sought after in a vegan diet.

In our modern culture, most mushrooms sold in supermarkets have been commercially grown in controlled mono-culture mushroom farms. Among the most popular are Swiss Brown, Portobello, and Shiitake, which have been carefully bred to ensure no toxic compounds still exist.

Separating edible from poisonous species requires meticulous attention to detail, as no single identifiable taxonomy exists separating the two varieties.

Medicinal Uses

Mushrooms have been used medicinally for thousands of years by various indigenous cultures. Different types of mushrooms have been used to trigger the immune system to fight against various viruses and bacteria, and in recent years, there have been studies in their efficacy against tumor growth. Stereotypically, they have been used to incite psychological effects, and recently, have been used in microdoses to treat anxiety and PTSD symptoms.

Mushrooms at RCG

Coffee and tea waste are the most abundant food waste on campus comprising about half of all waste we collect from Price Center. Coffee and tea wastes are suitable substrates for growing edible mushrooms mushrooms. Mushrooms can also be grown on compost from our composting program. This way we can turn wastes directly into food while also making a profit instead of paying for waste disposal.

The San Diego climate makes it difficult to grow mushrooms in the warmer months. Therefore, we decided to experiment growing edible fungi all year round inside of a humidified chamber.

We began by finding a naturally shaded spot in our garden behind our tool shed. The ground was leveled and a simple box with a hinged lid made of scrap lumber was built on top. We purchased inexpensive mist emitters and fitted them to an irrigation line with a timer.

For our first trial, we purchased King Oyster (Pleurotus Eryngii) and Almond Agaricus (Agaricus Subrufrescens) mushroom spawn. The Oyster spawn was mixed with coffee grounds, gypsum and lime in a cardboard box. The Agaricus spawn was mixed with fresh compost in trays and topped with a layer of peat moss and vermiculite to retain moisture. Unfortunately, the Almond Agaricus mycelium did not seem to colonize the substrate (we later discovered that we accidentally killed the mycelium). However, the King Oyster mycelium showed approximately 80-90% colonization of the substrate after two weeks of incubation, and we hope to get fruitbody production soon. The Almond Agaricus is promising for us because it tolerates warm weather and has an extremely fragrant almond aroma. There are many species of edible and medicinal mushrooms such as the Paddy-Straw Mushroom (Volvariella volvacea) and Pink Oyster (Pleurotus djamor) which also tolerate the warmer climate.

We are currently recruiting students who may be interested in this project which involves a variety of majors including microbiology, computer science/engineering, urban agriculture mycology and more. This is a great way for students to gain a unique hands on experience. Please contact Will at wtanaka@ucsd.ecu if you are interested.

RCG's preliminary attempts to grow mushrooms. Currently, they are being grown in the hoophouse as it is the only location in the garden that can sustain high enough humidities that most mushrooms require for propagation.