Oyster mushrooms on coffee grounds-Little experiment

In my opinion coffee grounds are perfect for making oyster spawn when using non-sterile techniques. However, in my experience, using them as a fruiting substrate never produced satisfactory results. They didn't fruit at all or produced nothing but crippled mushrooms. Usually the mycelium starts pinning but only produces some strange clumps that never develop into mushrooms.

Wheat straw however always works like a charm. Wheat straw works quick and provides perfectly normal fruits. Its only disadvantage is that it's very light. Meaning, by weight, one cannot get much substrate into small containers. So I decided to start a small experiment using coffee grounds as the major fruiting substrate, but topping it with a thin layer (about 1 inch thick) of wheat straw. The idea was that the wheat straw would produce normal oyster pins that then could profit from the heavier and nutrient rich coffee grounds. For fast results I used a relatively small jar with a capacity of only 500 ml. To compare the yields I also used a larger jar with a capacity of 1500 ml.

1st: Small jar experiment.

In order to get a evenly formed surface I only used the finer particles of my straw.

About 3 weeks later the first primordia appeared. Although still not perfect, part of the clump showed normal primordia.

2nd day:

3rd day: The majority of the pins have aborted. Only 4 of them had survived. Probably due to the small amount of substrate used.

4th day:

5th day: At this point the mushrooms were ready to harvest.The yield was rather disappointing. For a substantial amount of mushrooms one needs to make a lot of these jars.

2nd flush: The jars second flush. This time only 2 but larger and more healthy looking mushrooms.

3rd flush: Even though this flush started with more than 10 pins only 2 mushrooms made it to maturity. Obviously this small amount of substrate cannot support more than two mushrooms at a time.

2nd: Large jar experiment

This jar has a capacity of 1500 ml (still a rather low amount of substrate for growing oyster mushrooms) and isn't only wider but also a lot deeper. To provide the mycelium with enough air I applied three thin layers of wheat straw.

With this jar I used less spawn (about 20% of the substrate) and it took nearly 5 weeks for the first primordia to appear.

1st day:

2nd day:

3rd day:

4th day:

At this point I harvested the mushrooms. On the one part to prevent them from dropping spores and on the other part because it's winter and, as a result of the heating, the air in the room is rather dry. Resulting in cracked edges on the larger mushrooms. Nevertheless, in relation, this jar produced a higher yield, meaning that larger amounts of substrate always work better.

 

Conclusion: Although still not perfect, topping the coffee grounds with wheat straw produced quite normal mushrooms and can be a viable alternative for using wheat straw only. Nevertheless, as a fruiting substrate, I still prefer wheat straw. Wheat straw is more airy, holds more water and, in comparison, contains more lignin and cellulose, resulting in larger and better looking mushrooms. Although with straw it's better to use larger containers, it produces better results, causes less problems and is, especially for beginners, a better and fool proof alternative for coffee grounds or even sawdust.

It all depends on your goals. For sheer yields and ease of cultivation straw is always the better choice. But there are also people with a green lifestyle that want to recycle their coffee waste. No matter what the yields are. Adding a little wheat straw on top and into the substrate can prevent the problems occuring when using coffee grounds only.